LIACOS, J.

Ronald A. Cherubino, a licensed chiropractor, appeals to this court from a decision of the single justice affirming the decision of the Board of Registration of Chiropractors (board) that he had overutilized therapies in his practice of chiropractic medicine and had made improper charges, in violation of 233 Code Mass. Regs. §§ 4.06, 4.07(1) and (5), and in violation of G.L.c. 112, § 61 (1986 ed.). The board suspended Cherubino's license for three months, stayed the suspension, and imposed a two-year period of probation.

Cherubino claims that (1) the board's decision is unsupported by substantial evidence; (2) 233 Code Mass. Regs. § 4.06, proscribing "overutilization of practice," is unconstitutionally vague; (3) the board did not have authority to impose sanctions for violations of 233 Code Mass. Regs. § 4.06; (4) the board's decision was arbitrary and capricious; and (5) the board erred in refusing to admit in evidence a typewritten version of the chiropractor's handwritten patient progress notes and a chart summarizing the patient's treatment schedule. We conclude that there was no error, and we affirm the decision of the board.

On April 12, 1985, the board issued an order to show cause, questioning whether Cherubino overutilized his practice in his treatment of one Michael Ellis and whether the fees charged for Ellis's treatment were excessive. After a hearing on October 2, 1985, the board concluded that Cherubino was guilty of excessive utilization of therapies and improper charges in violation of 233 Code Mass. Regs. §§ 4.06, 4.07(1) and (5). The board also concluded at that time that there was no evidence of a violation of G.L.c. 112, § 61.

The plaintiff appealed to a single justice of this court who, on August 7, 1986, remanded the matter to the board for further findings. On January 28, 1987, the board conducted a second hearing at which it allowed the plaintiff to recreate that portion of his testimony given at the first hearing which was not transcribed properly, received certain exhibits in evidence, including the plaintiff's written progress notes, and excluded a typewritten transcription of the progress report and a chart summarizing the patient's treatment schedule. The board entered an amended decision and order on April 13, 1987, ruling that Cherubino's treatment was excessive in violation of 233 Code Mass. Regs. § 4.06, that his charges were excessive in violation of 233 Code Mass. Regs. § 4.07(1) and (5), and that Cherubino had violated G.L.c. 112, § 61, in that he was guilty of "deceit and gross misconduct in the practice of his profession." The board reimposed its prior order by suspending Cherubino for three months, but stayed the suspension and imposed probation for a period of two years. The single justice affirmed the amended decision on September 15, 1987, holding that there was substantial evidence to support the finding of the board.

We summarize the board's findings. Cherubino had been a licensed chiropractor in the Commonwealth for one and one-half years when Michael Ellis, a twenty-one year old man, first visited him for treatment on April 4, 1984. Ellis had been taken to Leonard Morse Hospital the previous day following a motorcycle accident, where he was examined, X-rayed, and discharged that same day with a diagnosis of cervical strain. Ellis complained to the plaintiff of pain in his neck and limited movement, and the plaintiff made a diagnosis of a so-called whiplash injury. He prescribed a program of treatment which included electrical stimulation to relieve muscle spasm, intersegmental traction, and heat, all of which are considered by the chiropractic profession to be "supportive procedures." Acute muscle spasms on such cervical whiplash injuries rarely last more than four to six weeks.

Cherubino administered forty-four treatments to Ellis between April 4 and October 15, 1984, thirty-six of which were exactly the same despite the fact that on May 7, 1984, he entered into the patient's progress report that the conditions were improving and that pain and spasm had been reduced. Cherubino charged $3,690 for the treatments. The board concluded that Ellis had suffered a mild-to-moderate whiplash injury which was not sufficiently serious to warrant continuous supportive treatment for six months.

1. Substantial evidence. The plaintiff contends that the board's decision is unsupported by substantial evidence. Substantial evidence is "such evidence as a reasonable mind might accept as adequate to support a conclusion." G.L.c. 30A, § 1 (6) (1986 ed.). New Boston Garden Corp. v. Assessors of Boston, 383 Mass. 456, 466 (1981). Our review under the substantial evidence standard is circumscribed. Langlitz v. Board of Registration of Chiropractors, 396 Mass. 374, 379 (1985). "While we must consider the entire record, and must take into account whatever in the record detracts from the weight of the [board's] opinion, Cohen v. Board of Registration in Pharmacy, 350 Mass. 246, 253 (1966), as long as there is substantial evidence to support the findings of the [board], we will not substitute our views as to the facts." Arthurs v. Board of Registration in Medicine, 383 Mass. 299, 304 (1981). See Bill v. Board of Registration of Chiropractors, 394 Mass. 779, 781 (1985). We conclude that the board's decision was supported by substantial evidence.

The board took testimony from two expert witnesses. Allan R. Steingisser found that the supportive procedures were not consistent with the diagnosis or the findings between April 4 and June 8, 1984. Charles B. Johns testified that the treatments given by Cherubino were excessive after the initial four to six weeks and were not reasonable or necessary.

Cherubino argues that the board could not rely properly on the opinions of these experts because they were formed without the benefit of Cherubino's patient progress notes. These experts based their conclusions on Ellis's medical records, including the hospital report relating to his injury and Cherubino's letters to the insurance company describing the patient's progress. Cherubino's medical report of April 10, 1984, included the results of his orthopedic examination, neurological examination, and X-ray examination, as well as his clinical comments, diagnosis, and recommendation for treatment. His letters of May 7 and June 13, 1984, noted that the patient's pain and spasm had been reduced and that the range of motion had improved. The fact that Johns and Steingisser did not have the patient progress notes before them when they formed their judgment does not negate their testimony. The board admitted Cherubino's handwritten progress notes in evidence, expressly finding that these notes were consistent with Johns's testimony that Ellis's condition did not warrant continuing the therapy. The board "is free to evaluate evidence in light of its own technical expertise." Langlitz v. Board of Registration of Chiropractors, supra at 381. The board, after engaging in its own evaluation of the progress notes as well as the other evidence before it, could conclude that the forty-four treatments in six months were not justified by the patient's condition.

Cherubino testified that Ellis's continued complaints of pain due to racquetball necessitated further treatment. In its decision, the board "discounted" this testimony "in large part, both in light of all the other evidence presented and by [its] opinion of the credibility of the witnesses before it." "Credibility of witnesses is for the agencies . . . and the agency has the benefit of observing the witnesses in judging credibility." Vaspourakan, Ltd. v. Alcoholic Beverages Control Comm'n, 401 Mass. 347, 352 (1987). The board, and not this court, has the responsibility of deciding preliminary questions of credibility and the weight of the evidence; the board was not required to believe all of the plaintiff's testimony. Maddocks v. Contributory Retirement Appeals Bd., 369 Mass. 488, 495 (1976).

The references to racquetball in the written progress notes compiled by the plaintiff did not compel the board to find that the patient required the additional treatment. The board was not required to grant credence to every entry the plaintiff had made in his written progress notes. The board was free to accept as true only a portion of the plaintiff's handwritten progress notes. The board "may disbelieve the whole or a part of a party's [or witness's] testimony, even where it is uncontradicted." Calderone v. Wright, 360 Mass. 174, 176 (1971), quoting Lydon v. Boston Elev. Ry., 309 Mass. 205, 206 (1941). See P.J. Liacos, Massachusetts Evidence 131 (5th ed. 1981).

2. Vagueness. The plaintiff claims that 233 Code Mass. Regs. § 4.06 is unconstitutionally vague. We disagree.

"'A law is void for vagueness if persons "of common intelligence must necessarily guess at its meaning and differ as to its application."' Caswell v. Licensing Comm'n for Brockton, 387 Mass. 864, 873 (1983), quoting Connally v. General Constr. Co., 269 U.S. 385, 391 (1926). '. . . [S]tatutes that do not define or relate to criminal conduct need not be drawn as precisely as statutes that touch upon criminal acts. . . . [If] neither First Amendment freedoms nor criminal conduct are concerned . . . we limit out vagueness analysis to whether [the statute or regulation] is unconstitutionally vague as applied in [the particular] case. . . .' Caswell, supra. Aristocratic Restaurant of Mass., Inc. v. Alcoholic Beverages Control Comm'n (No. 1), 374 Mass. 547, 552, appeal dismissed for want of a substantial Federal question, 439 U.S. 803 (1978)." Gurry v. Board of Pub. Accountancy, 394 Mass. 118, 127 (1985). Because suspension of a chiropractor's license is not penal or criminal in nature, id., we apply the less strict civil standard in our analysis of 233 Code Mass. Regs. § 4.06. Lapointe v. License Bd. of Worcester, 389 Mass. 454, 462 (1983), citing Caswell v. Licensing Comm'n for Brockton, supra.

Title 233 Code Mass. Regs. § 4.06 defines "[o]verutilization of practice" as "practice excessive in quality or amount to the needs of the patient." As applied to the facts of this case, as found by the board, this regulation could be understood without any guesswork. "Persons of common intelligence" could conclude easily that a patient with an injury that normally required from four to six weeks of treatment did not need forty-four separate treatments over a six-month period, absent proven exceptional circumstances.

Title 233 Code Mass. Regs. § 4.06, when read in context, also gives a practitioner guidance. Title 233 Code Mass. Regs. § 4.03 provides, in part, that "[s]upportive procedures shall be supplemental or ancillary to the chiropractic adjustment and must not be used as an independent therapy. The use of supportive procedures MUST AT ALL TIMES be supported by a clinical rationale equivalent to present additional standards as well as usual and customary practices" (emphasis in original). Read together, §§ 4.06 and 4.03 put the practicing chiropractor on notice that when supportive procedures are administered, they must be justified by the clinically diagnosed needs of the patient and may not constitute the primary form of therapy. The board found that Cherubino repeatedly treated his patient with the same three costly supportive procedures without furnishing sufficient justification. A person of common intelligence would have known that such behavior was within the scope of activity proscribed by 233 Code Mass. Regs. § 4.06. We note that the standard in this case — treatment not "excessive in quality or amount to the needs of the patient" — is certainly clearer than the regulation which disciplined accountants for acts "discreditable to the profession," which the court in Gurry, supra at 126-127, refused to hold unconstitutionally vague.

3. The board's authority to issue sanctions. The plaintiff argues that the board lacks authority to impose sanctions for violations of 233 Code Mass. Regs. §§ 4.06 and 4.07. We disagree.

"An agency . . . has considerable leeway in interpreting a statute it is charged with enforcing." Grocery Mfrs. of Am., Inc., v. Department of Pub. Health, 379 Mass. 70, 75 (1979). See Manning v. Boston Redevelopment Auth., 400 Mass. 444, 453 (1987). The board properly could conclude, on remand by the single justice, that "[o]verutilization of practice" and "[i]mproper charges" are forms of deceit or gross misconduct subject to discipline under G.L.c. 112, § 61. See Leigh v. Board of Registration in Nursing, 395 Mass. 670, 675 (1985).

The board's regulations must bear only a rational relation to the enabling statute. Citizens for Responsible Envtl. Management v. Attleboro Mall, Inc., 400 Mass. 658, 669 (1987). Levy v. Board of Registration Discipline in Medicine, 378 Mass. 519, 524 (1979). "[T]he Legislature through the board has provided for the imposition of sanctions 'to protect the life, health and welfare of the people at large and to set up a plan whereby those who practice [chiropractic] will have the qualifications which will prevent, as far as possible, the evils which could result from ignorance or incompetency or a lack of honesty and integrity.'" Keigan v. Board of Registration in Medicine, 399 Mass. 719, 722 (1987), quoting Matanky v. Medical Examiners, 79 Cal.App.3d 293, 305 (1978). Imposing sanctions for excessive treatment and charges bears a rational relation to the Legislature's goal of safeguarding the public welfare through regulation of the chiropractic profession.

4. Was the board's action arbitrary or capricious? The plaintiff maintains that the board's amended decision was arbitrary and capricious because it reversed its earlier finding that there was no evidence of a violation of G.L.c. 112, § 61.

The board's amended finding of a violation of G.L.c. 112, § 61, when it originally failed to make this finding, does not constitute an arbitrary or capricious action. The board states in its amended decision that its failure to find violation of § 61 was "inadvertent." There is nothing in the record to refute this statement.

General Laws c. 112, § 61, authorizes the board to suspend or revoke the license of a practitioner who is found to be guilty of "deceit [or] . . . gross misconduct in the practice of his profession." A violation of 233 Code Mass. Regs. §§ 4.06 and 4.07 falls within the conduct proscribed by G.L.c. 112, § 61. The board was not required to show additional wrongdoing on the part of the chiropractor to justify its imposition of sanctions. Where there is substantial evidence in the record to support the board's decision, we conclude that it was not arbitrary or capricious as matter of law. See Massachusetts Elec. Co. v. Department of Pub. Utils., 376 Mass. 294, 312 (1978).

5. Exclusion of two documents. The board did not err in excluding the typewritten transcription of Cherubino's handwritten patient progress notes and the chart summarizing the patient's visits to his office, both prepared by his counsel. The board did admit the handwritten notes in evidence, and they appear to us to be sufficiently legible. The board was within its discretion to exclude the verbatim transcription and the chart, both of which it had admitted as chalks. Dyecraftsmen, Inc. v. Feinberg, 359 Mass. 485, 487 (1971). P.J. Liacos, Massachusetts Evidence 403-404 (5th ed. 1981).

The matter is remanded to the single justice, and a judgment affirming the decision of the board is to be entered.

So ordered.