The Philadelphia 76ers opened a 20-point lead in the first two minutes of the second quarter, and with Andrew Toney scoring 23 points defeated Boston, 116-98, yesterday at Boston Garden, ending the Celtics' winning streak at 18 games.

"They played the game today the way we played the last 18 games," Boston's Larry Bird said.

Boston's last loss came on Feb. 21 in Seattle. The Celtics remained tied with the 1969-70 New York Knicks for the NBA's third-longest winning streak.

The Celtics' nine-game home winning streak over Philadelphia also was ended. The 76ers won one week after losing to Boston at Philadelphia, 123-111.

Boston Coach Bill Fitch said, "As long as we had to lose, I'm glad it was to Philadelphia . . . If you've got to get beat, get beat by the best.

"It was typical of our streak. We have one loss in a row now, and, like the win streak, it was a great team effort. This game belonged to Philadelphia and we're not making any excuses."

Philadelphia led, 26-15, after the first quarter as Boston made 25 percent of its field goal attempts. The 76ers started the second quarter with nine straight points, building their lead to 35-15 with 10:31 left in the first half.

Mike Bantom started the run with a three-point play, and followed with a tip-in. Julius Erving (21 points) ended a fast break with a dunk, and Darryl Dawkins scored on a 12-foot jumper.

Philadelphia led, 57-44, at halftime, and built its biggest lead with an 8-2 run to make the score 107-81 midway through the final period. Toney scored six of those points.