Montgomery County District Court Judge Henry J. Monahan, who was acquitted in August of charges of breaking into a house in Hagerstown and assaulting two police officers, will return to the bench on Monday, the chief judge of the Maryland District Court system said yesterday.

Monahan won acquittal in the court case after mounting an unusual defense, arguing that his erratic behavior in the early morning incident on May 3, 1985, was caused by a mild stroke that left him confused.

After that acquittal, District Court Chief Judge Robert F. Sweeney asked the state Commission on Judicial Disabilities to investigate Monahan's health and judicial competence. The commission this week ended its probe and cleared Monahan.

"On the basis of independent medical testimony, the commission has decided that there is no justification for further proceedings. The case is closed," Howard E. Wallin, executive secretary of the seven-member commission, wrote in a prepared statement.

Monahan's duties have been restricted to administrative tasks since he was charged last May.

Monahan, 53, was attending an annual statewide conference of jurists in Baltimore yesterday and could not be reached for comment.

William Rowan III, a Montgomery lawyer who defended Monahan in court, issued a prepared statement.

"The judge wishes to thank his friends and the many members of the [Maryland, Montgomery and D.C.] bar who have stood by him while this matter has been under review. He is prepared to resume his full duties as assigned to him by the court," the statement said.

In a telephone interview from his Baltimore home, Sweeney criticized the commission for taking so long to clear Monahan.

"I am distressed at the length of time that it took the commission to reach its judgment," he said. "I know that the commission is composed of highly competent and busy judges and nonjudges who give the citizens of Maryland of their time without remuneration, but it seems to me that the public interest would be better served by a process that did not take nine months for an examination to be made of medical records."

"I was perfectly satisfied with the correctness of [the court's not guilty] decision," said Sweeney, a longtime friend of Monahan's. "I had formed that independent layman's opinion many months ago, but I thought our citizens were entitled to have a professional medical opinion as to the state of Judge Monahan's health."

Monahan's trouble began last May when the annual jurists conference was being held in Hagerstown.

According to police records and testimony at the trial, Monahan was arrested at a house near the Holiday Inn there. He resisted two police officers who tried to subdue him.

Hospital records introduced at the bench trial showed that Monahan had a blood alcohol level of .22 percent. A person with a level of .13 percent is considered intoxicated under Maryland law.

The arrest surprised other judges and lawyers who said Monahan seldom had more than one or two drinks.

Judge Edward O. Thomas, after hearing two doctors who treated Monahan testify that his disorder was an uncommon form of amnesia caused by a small brain stem stroke, found him not guilty of the charges.