John A. Paisley, a former high-level CIA employe described as an expert sailor, has been missing since Sunday when he was seen sailing alone in his 31-foot sloop across Chesapeake Bay, Maryland marine police reported.

Paisley's boat, the Brillig, unoccupied but its sails still set, was found the following morning where it had run aground near Point Lookout at the mouth of the Potomac River.

Paisley, 55, who retired in 1974 as deputy director of the CIA's Office of Strategic Research, was last seen Sunday afternoon sailing west across the bay from Hooper Island toward his home morning at Solomons, Md.

Following discovery of the empty sailboat the next morning, the Coast Guard began an extensive search involving three helicopters, two "utility" power boats and a Coast Guard cutter. That search was discontinued Tuesday night after no trace of Paisley was found, but Maryland marine police continue to search waters near the mouth of the Potomac.

Paisley, who for the past six months has worked as a consultant for the accounting firm of Coopers and Lybrand, was an expert sailor who once lived aboard his sailboat for more than two years according to his estranged wife, Maryann Paisley of McLean.

Paisley was also an expert swimmer and scuba diver, capable of swimming several miles, she said.

Phil Wagoneer, a close friend of Paisley and a CIA employe, said yesterday that Paisley was sailing the Brillig on Sunday alongside another sailboat until the late afternoon. The second boat returned to its mooring at Solomons, Wagoneer said, and Paisley radioed at 6 p.m., saying he was coming home after dark.

The Coast Guard reported light winds and three-to-four-foot waves on the bay Sunday evening.

Paisley's boat was found near Point Lookout with its shorwave radio on, according to his wife. She said the steering mechanism on the sailboat was not locked into position.

Referring to speculation that Paisley may have fallen overboard while adjusting sails, his wife said that in several years of sailing she had never seen her husband tend the sails without locking the wheel. "He was a cautious, level-headed sailor," she said.

The boat's running lights were off when found, according to the Coast Guard. Wagoneer, also an experienced sailor, said that fact probably means Paisley left his boat before dark - about an hour after his last radio communication.

John Harpold of the marine police said yesterday that drowning victims in the area of Chesapeake Bay where Paisley was last heard from are usually discovered within a few days because of the hight volume of water traffic in the area.

"If the body is there, somebody is going to find it," Harpold said.

Paisley, who recently separated from his wife, lived at 1500 Massachusetts Ave. NW. He has two children, Diane, 20, and Edward, 21.