
393 Mass. 117 (1984)
469 N.E.2d 819
PATRICIA FIELD
vs.
MASSACHUSETTS GENERAL HOSPITAL & others.[1]
Supreme Judicial Court of Massachusetts, Suffolk.
September 10, 1984.
October 3, 1984.
Present: HENNESSEY, C.J., LIACOS, NOLAN, LYNCH, & O'CONNOR, JJ.
Benjamin W. Moulton for the plaintiff.
Jared H. Adams for Thomas B. Fitzpatrick.
David M. Gould for John A. Parrish.
O'CONNOR, J.
In 1978, the plaintiff began an action in Superior Court against the Massachusetts General Hospital (MGH) and Doctors Parrish and Fitzpatrick for injuries resulting from her participation as a paid volunteer in a medical research experiment designed to find a cure for psoriasis. She alleged four counts: negligence, misrepresentation, assault and battery, and breach of warranty. Pursuant to G.L.c. 231, *118 § 60B, the Superior Court convened a medical malpractice tribunal which directed dismissal of all counts against the doctors, and of two counts against MGH, unless the plaintiff posted bond. The plaintiff did not post bond, and a Superior Court judge allowed the doctors' motions to dismiss with prejudice. Two counts against MGH remained viable.
In July, 1983, pursuant to Mass. R. Civ. P. 60 (b) (4) and (6), 365 Mass. 828 (1974), the plaintiff, by new counsel, requested that the Superior Court vacate the judgments in favor of the doctors. Rule 60 (b) provides that "[o]n motion and upon such terms as are just, the court may relieve a party ... from a final judgment ... for the following reasons: ... (4) the judgment is void; ... or (6) any other reason justifying relief from the operation of the judgment." In her motion the plaintiff contended, inter alia, that because she was not a "patient who was engaged in treatment" the medical malpractice tribunal "did not have subject matter jurisdiction over [her] causes of action..., and the decision of the Tribunal ... as well as the Judgments which were entered thereon are void and a nullity and should be set aside."
Stating that "[u]nder Mass. R. Civ. P. 60 (b) (4), the judgment of the Medical Malpractice Tribunal is void," a Superior Court judge vacated the judgments and reported two questions to the Appeals Court. See G.L.c. 231, § 111. The judge took no action on the motion in so far as it sought relief under rule 60 (b) (6), nor did his report address the plaintiff's rule 60 (b) (6) arguments. We granted the plaintiff's petition for direct appellate review. We reverse.
Rule 60 (b) (4) allows relief only from void judgments. A court must vacate a void judgment. It may not vacate a valid one. No discretion is granted by the rule. See Reporters' Notes to Mass. R. Civ. P. 60 (b) (4), Mass. Ann. Laws, Rules of Civil Procedure at 586 (1982).
The plaintiff argues that because the medical malpractice tribunal "did not have subject matter jurisdiction" the judgments entered in the Superior Court are void. But she errs, as did the Superior Court judge, by focusing on the tribunal's authority. Rule 60 (b) (4) concerns the authority of courts. The Superior *119 Court had  and indeed still has  jurisdiction over the plaintiff's civil action. "Jurisdiction concerns and defines the power of courts, encompassing the power to inquire into facts, apply the law, make decisions and declare judgment." Police Comm'r of Boston v. Municipal Court of the Dorchester Dist., 374 Mass. 640, 662 (1978). Since the Superior Court had the authority to declare the judgments, they are not void, and rule 60 (b) (4) affords the plaintiff no relief.
The plaintiff's real complaint is that the Superior Court judge erred by convening the medical malpractice tribunal. We express no opinion about that contention except that it is not relevant to a rule 60 (b) (4) motion. "A void judgment is to be distinguished from an erroneous one...." Lubben v. Selective Serv. Sys. Local Bd. No. 27, 453 F.2d 645, 649 (1st Cir.1972).
Because the Superior Court judge did not address the plaintiff's rule 60 (b) (6) argument, we do not reach it. Nor need we reach the reported questions. See McStowe v. Bornstein, 377 Mass. 804, 805 n. 2 (1979). We reverse the order of the Superior Court judge vacating the judgments entered in favor of the doctors, and remand the case to the Superior Court for further proceedings not inconsistent with this opinion.
So ordered.
NOTES
[1]  John A. Parrish, M.D., and Thomas B. Fitzpatrick, M.D.
