A Naval Academy midshipman accused of stealing more than $8,000 worth of goods from an academy store disappeared hours before his court-martial was scheduled to begin yesterday.

Clayton Matthew Lewis, 20, of Roanoke Rapids, N.C., is now considered absent without leave. Academy officials, who said they had no idea where Lewis had gone, delayed the court-martial and said they would notify Navy intelligence units in Washington.

Lewis, who has completed two years at the academy, is only the third midshipman to face a court-martial in this century. He was charged in May with an unauthorized absence from the academy, and later with larceny, conspiracy to commit larceny, and receipt of stolen goods.

If convicted, Lewis faces up to 11 1/2 years at hard labor, forfeiture of all his pay and dismissal from the Navy.

Academy spokesman Dennis Boxx said the charges against Lewis center on the theft of about $8,000 worth of clothing, record albums and appliances from the academy's store between August 1984 and April 1985. Academy officials believe one other midshipman was involved, Boxx said. That midshipman was not charged, but he was scheduled to testify during the court-martial.

Academy officials would not say how the goods were allegedly stolen, but they did say that Lewis did not work at the store.

Lt. Christine Senseman, the Navy Legal Services officer representing Lewis in the court-martial, would not comment on the case.

This is not the first time Lewis has left the academy without authorization, according to Boxx. He said Lewis was absent without leave for 16 days in May. When he returned to the academy and turned himself in, Boxx said, he was charged with unauthorized absence and ordered confined at the U.S. Marine base at Quantico.

However, a military judge ordered Lewis returned to the academy three days later. He was restricted to academy grounds and ordered to report every two hours between 6:45 a.m. and midnight.

On July 16, after an investigation led by Marine Corps Maj. Harvey A. Hopson, an instructor in the academy's law department, Adm. Charles R. Larson, the academy superintendent, ordered Lewis court-martialed on the larceny charges.

Boxx said Lewis failed to report as scheduled at 8 p.m. Monday and has not been heard from since. The academy grounds were searched to no avail, officials said. Midshipmen generally pass freely through the gates of the walled campus.

Lewis' parents, who live in Roanoke Rapids, could not be reached for comment yesterday.

Richard Curran, an editor of the Roanoke Rapids Daily News who has met Lewis, said the midshipman comes from a family that is "not well-to-do." Lewis, who was nominated to the academy by Sen. Jesse Helms (R-N.C.), was described by Curran as a basketball player and an outstanding student.

The other two courts-martial at the Naval Academy in this century took place in 1922 and in 1981, with both defendants being found guilty. In the most recent case, Midshipman Michael R. Olmstead was found guilty of involuntary manslaughter after an auto accident on the academy grounds in which another midshipman was killed.

Olmstead, who argued that he was not driving the car, was convicted and sentenced to dismissal from the academy. The sentence was suspended, and he was allowed to graduate after a four-month probationary period.