Washington Bullet center Rick Mahorn, who had been struggling against Artis Gilmore, slapped the ball away from the 7-foot-2 Chicago center with the Bullets clinging to a two-point lead in the final 20 seconds last night, and they went on to a 93-90 victory at Capital Centre.

The Bullets, playing before 6,234, were ahead, 92-90, when the ball went in to Gilmore. Four Bullets collapsed around him and Mahorn knocked the ball away as Gilmore turned to the basket.

Frank Johnson picked up the loose ball and was fouled by Chicago's Ronnie Lester. Johnson made one of two free throws with 15 seconds to play, but the Bulls still almost pulled it out.

Greg Ballard, who led the Bullets with 20 points and 13 rebounds, stole the ball from Ray Blume and went in for a dunk. He missed, however, and the ball bounded high off the rim to Blume near midcourt. Blume passed to Reggie Theus, whose frantic three-point attempt was short as the game ended.

"Artis is so strong, there isn't much you can do against him," said the 6-9 Mahorn. "I know he wants to go to his left, so on that last play, I forced him that way and got over in front of him and he turned right into me and exposed the ball. I grabbed at it."

The Bulls went into the fourth quarter with a 69-68 lead and made it obvious that they were going to go to Gilmore every chance they got.

Finesse isn't Gilmore's game; he usually got the ball low on the right side of the lane and turned and put it in the basket. He had 11 of his 20 points in the period, but with four Bullets around him every time he touched the ball in the final minute, Gilmore missed two shots and had the ball stolen.

"Late in the game we collapsed in our legal position," said Bullet Coach Gene Shue, alluding to his team's attempts to double-team without being called for an illegal zone defense. "They weren't going to beat us by Gilmore turning inside and just dropping the ball in. We were going to make them hit the outside shot. If they hit those, we would have accepted it."

Gilmore's layup, followed by a 17-footer by Lester and a layup by Theus, gave the Bulls an 81-75 lead with 7:39 remaining.

Don Collins scored on a layup for the Bullets, but Gilmore's hook on a power move kept the Bulls' lead at six.

The Bullets responded with nine straight points to take an 86-83 lead with 3:48 left.

Jeff Ruland had two points and Frank Johnson three.

Gilmore made a layup to get the Bulls back to within one, and after a basket by Mahorn, Gilmore made a three-point play to tie the score at 88 with 2:21 left.

A goal-tending call against Gilmore on a shot by Collins gave the Bullets a 90-88 advantage. Lester and David Greenwood each made one free throw around two by Ruland for a 92-90 Bullet lead.

Gilmore had 13 rebounds and five blocked shots and was trouble for the Bullets all night.

Ricky Sobers, who beat the Bullets with a last-second, 20-foot jumper three weeks ago, was on the bench in his street clothes because of a sprained ankle. Thus, the Bulls didn't have the outside shooter to take the pressure off Gilmore and the Bullets were able to collapse on him.

Theus, who made a three-point field goal in the first half, was held to two points in the fourth period.

"We overplayed him and didn't let him get the ball," said Shue.

Elsewhere in the NBA, John Drew scored 26 points for the Atlanta Hawks, who gave the host Philadelphia 76ers their fifth loss in the last seven games, 96-90.

Bob Lanier scored a season-high 26 points to lead the Milwaukee Bucks to a 122-118 victory over the visiting Boston Celtics; Kareem Abdul-Jabbar had 30 points as Los Angeles defeated the Pacers in Indianapolis, 97-92; in San Antonio, George Gervin scored 32 points and the Spurs routed Houston, 128-90; Kansas City defeated visiting New Jersey, New Jersey, 114-104, and in Denver, Kiki Vandeweghe scored 24 points and the Nuggets beat the Dallas Mavericks, 128-113.

Gus Williams' 42 points led host Seattle over Utah, 115-103; Michael Brooks had 21 points and 14 rebounds in San Diego's 117-108 victory over visiting Cleveland; Bernard King's jumper with one second left gave host Golden State a 104-102 win over the New York Knicks.