Washington held off the Philadelphia 76ers for 3 1/2 quarters last night. But when the game was at stake, the visitors had the big plays and beat the Bullets for the sixth straight time, 100-96.

The defeat ended all hope of the Bullets finishing with the fourth-best record in the Eastern Conference, and it set up a critical season-ending game against Atlanta Sunday at Capital Centre. The loser of that game will finish in the sixth playoff spot and have to face Philadelphia in the first round of the playoffs.

The Hawks beat Indiana, 109-91, last night, and they and the Bullets have 42-39 records.

New Jersey beat Boston, 113-96, last night, giving the Nets a 43-38 record. Because they won the season series against the Bullets, even if they lose to Detroit in their final game tonight and the Bullets beat the Hawks, the Nets would get fourth and have the home-court advantage in the first round of the playoffs against the fifth-place Bullets.

The Hawks can finish fourth if New Jersey loses to Detroit and they beat the Bullets, but will finish sixth if they lose to the Bullets, no matter what the Nets do.

The Bullets came close last night, and had the third sellout crowd of the season at Capital Centre, 19,035, cheering much of the game.

Lionel Hollins' 19-foot jump shot with 20 seonds to play broke a 96-96 tie and proved to be the winning points.

"We had control most of the game," said Bullets Coach Gene Shue. "It just seems that when we play the better teams and the game comes down to the fourth quarter, the defense tightens and we have trouble scoring."

The Bullets led by 10 points much of the second and third periods and had a nine-point lead, 85-76, with 8:48 to play. They made only four of their last 13 shots, however, and the 76ers charged past them.

The 76ers took the lead for the first time since the first period when they scored seven straight points, four coming from Darryl Dawkins, to turn an 89-84 deficit into a 91-89 advantage with 3:31 remaining.

Dawkins started the rally with a layup. Then, after stealing Spencer Haywood's pass, he scored on a turnaround jumper as Rick Mahorn fell on him. Dawkins missed the free throw, but Andrew Toney got the rebound and Julius Erving slam dunked his own missed shot as he was fouled by Jeff Ruland. He made the free throw for a two-point lead.

Don Collins' driving layup around Hollins with 35 seconds left tied the score at 96.

The 76ers tried to set up Toney, but he was double covered. The ball went to the open Hollins, and he made a 19-footer with Ruland jumping at him.

The Bullets' chance to tie ended when Frank Johnson's 22-footer with four seconds left bounded off the rim to Dawkins. He was fouled by Collins with two seconds left and made two free throws.

"We played a hard game and played good defense the whole game," said Shue. "That's what you have to do with Philadelphia. You can't let them beat you with the break and we didn't. (Philadelphia scored only seven points off the fast break, the Bullets six.)"

The victory was a big one for the 76ers, as it clinched the second-best record in the conference, which means they will have the homecourt advantage in every conference series they play except against the Celtics.

Erving, who played like a mortal except on his big three-point play in the final quarter and on a couple of fancy moves early, led the 76ers with 22 points. Dawkins, in his fourth start since being activated March 24 after missing 28 games with a broken right leg, scored 18.

Ruland led the Bullets with 22 and Haywood had 20.

Elsewhere: In Atlanta, the Hawks beat Indiana, 109-91; the Chicago Bulls sent visiting Cleveland to its 18th straight defeat, 112-102; In Dallas, San Antonio clinched the divisional title with a 118-106 win over the Mavericks; in Kansas City, the Kings edged Denver, 123-121, and Phoenix defeated the Trail Blazers in Portland, 113-99.

The Milwaukee Bucks beat the visiting New York Knicks, 112-99; the Houston Rockets defeated the visiting Utah Jazz, 107-100, and the Los Angeles Lakers beat the visiting Golden State Warriors, 125-109.