The Boston Celtics showed again tonight that when they come to play, the Houston Rockets are no match for them, no matter how much the Rockets believe in themselves.

This was a Celtic game if ever there was one as Boston controlled the boards, ran fast break after fast break and had the Rockets reeling and backpedaling all game long as the Celtics frolicked to a lopsided 109-80 victory in front of 15,320 delirious fans at Boston Garden to take a 3-2 lead in the best-of-seven NBA championship series.

Game 6 will be played in Houston Thursday and will be televised live in Washington (WDVM-TV 9 at 10 p.m.).

"Tonight was more of a Celtic game than a Rocket game," said Boston Coach Bill Fitch.

It certainly was as the Celtics took off quick and never looked back. Every time the Rockets gave them an opening, they took it and, zoom, were gone.

"When we get in a transition game and run like we did tonight, there's no team in basketball that can ply with us," said Cedric Maxwell, who led the Celtics with a marvelous 28-point, 15-rebound game. He made 10 of 13 shots from the field. Every Celtic played and scored at least two points as Boston became the firest team in the series to score 100 points in a game.

Four other Celtics scored in double figures, with Robert Parish getting 18.

Larry Bird had his third straight off game scoring, making only five of 16 shots, but once again he did the other things, getting 12 rebounds and eight assists.

Houston's only threat was Moses Malone and he was held to 20 points and 11 rebounds.

As a team, the Rockets shot only 36 percent.

"We got beat in all categories," said Houston Coach Del Harris. "We didn't shoot well and we didn't handle the ball well. It was a complete disaster. It was a total breakdown of what we wanted to do."

What the Rockets did was get behind early and then, for the first time in the series, got caught up in a running game and that spelled curtains.

"It's tough for us to play catch up," said Houston's Billy Paultz. "This game was just like Saturday's game when we got blown out. We started out bad and got worse. They kept us off the offensive boards and got the defensive rebounds they needed to get the fast breaks and they certainly took advantage of them."

Boston had 32 fast-break opportunities and turned them into 33 points.

The Celtics blew the game open with a 19-1 scoring spurt late in the first quarter that staked them to a 59-37 halftime lead.

They got their first 29-point lead in the third period and, even though Fitch substituted freely and the Celtics even appeared to lose interest for a few minutes, they had too much going for the Rockets to ever make a serious challenge.

"Sometimes you win by four, sometimes you win by five, sometimes you win by a million," said Harris. "Tonight they won by a million."

The Rockets played only six men in the fourth game of the series Sunday in Houston and came away with a 91-86 victory to even the series at 2-2. Mike Dunleavy was the hero that game with 28 points.

Dunleavy was no hero ton ight and the six iron men turn ed into 11 paper soldiers. Harris used nine players in the first half and, before the game was over, everyone in a red uniform had played -- and scored.

Dunleavy made only one of five shots, scored five points and fouled out after playing only 14 minutes.

"They went to the boards and we stood around and never got involved," said Malone.

During one timeout late in the game a Celtic fan behind the Rockets bench yelled at Harris -- "This is the gong show . . . Gong!"

Boston scored the first six points of the game, but Houston came back with eight straight. The lead changed sides six times after that before the Celtics took of their 19-1 spurt.

Bird started it with a 15-footer and Maxwell ended it with a twisting reverse layup that resulted in a three-point play. It was set up when Parish, even though he had two fouls that early in the game, went up and smacked Bill Willoughby's dunk attempt away, sending the shooter on the seat of his pants.

Parish, who continually beat Malone up the floor, had eight of his 12 first-quarter points in the spurt. Maxwell had five of the points and two assists.

"Cedric is playing like he wants to win this whole thing by himself," said teammate Chris Ford. "He's going after every rebound and every loose ball."

Four of Maxwell's 10 field goals came after he grabbed an offensive rebound.

"I think I'm too quick for the two guys who are guarding me," he said, referring to Paultz and Malone.

"I'm always moving without the ball and sliding in and out of the lane, looking for the nooks and crannies.

"We all read a few things the Rockets said about us in the papers, like we were an average team and that they were going to be very physical against us," Maxwell added. "Yeh, that was somewhat of an incentive. It was like a challenge and you don't challenge the Celtics.

"We were anxious for the game to get started. We just ran, controlled the boards and got up on them on defense and just kept pouring it on."

Calvin Murphy, the Rockets' hyper-high-scoring sixth man who has had trouble finding the basket all series along, bruised his shoulder in the second period and spent the second half slumped over on the bench with his left arm strapped to his side. He is doubtful for Thursday's game.

If a seventh game is necessary, it will be played Sunday afternoon at Boston Garden.