Georgetown hit the Big Apple in grand style tonight, routing nationally ranked St. John's, 72-42, before an awe-struck sellout crowd of 19,591 at Madison Square Garden.

The Hoyas (12-2) used their 11th straight victory as a showcase for their talent, and it was such a remarkable performance that it will probably have reverberations all through the East--and even farther.

The Hoyas, ranked ninth and 13th in the wire service polls, were that good tonight after Wichita State defeated Iona, 97-78, in the first game of the doubleheader.

This was supposed to be Georgetown's first major test of the season, playing away from home in a city known for its distractions, in a storied building and against a good opponent in the Big East Conference opener for both teams. The Hoyas quickly turned it into a colossal mismatch.

Lou Carnesecca, the St. John's coach, didn't hold back on any superlatives, although Georgetown Coach John Thompson did.

"That was one of the great, great performances," Carnesecca said. "They did it all ways, both offensively and defensively. We were stunned. They were awesome. People are going to remember this game for a long time, and so am I."

Eric (Sleepy) Floyd scored on a breakaway basket off the opening tap and the Hoyas never even so much as glanced over their shoulders after that. They built a 41-9 lead late in the first half.

St. John's (9-2), ranked 18th and 20th in the polls came into the game with a six-game winning streak after impressively winning the Holiday Festival here last week. But the Redmen looked lost against the Hoyas' full-court pressure and their motion offense. They looked as if they had no clue what to do at either end of the floor. They had no antidote for Georgetown's quickness.

It seemed that whenever the Redmen shot the ball, a Hoya blocked it; when they tried to dribble it, a Hoya stole it, and when they tried to pass it, a Hoya usually knocked it away.

The Hoyas, meanwhile, kept on pressing, running and subbing.

Floyd led all scorers with 16 points and Eric Smith had 14. Pat Ewing was in foul trouble much of the game and played only 19 minutes, but the 7-foot freshman had nine points, six rebounds and five blocked shots, four in the first half.

Georgetown had an 8-2 lead when Ewing blocked a shot by Chris Mullin, knocking the ball to Fred Brown. Ewing then sped up court on the right sideline. Brown took two dribbles and lobbed a long pass that first appeared to be nowhere near Ewing. But he leaped over three defenders, grabbed the ball eight feet from the basket and dunked it, all before any of the startled Redmen even turned around.

By the time the score was 26-4, seven Hoyas had scored.

This was Georgetown's night.

Thompson said this was the best his team has played so far this season, but quickly added, "We still have a long way to go. St. John's is a lot better than the score indicated. . . This game wasn't reflective of how we always play. This is just one game."