Karl Wallenda, 73, the daredevil of the high wire, plunged 10 stories to his death yesterday while attempting to walk a tightrope between two hotel towers on the beachfront of San Jaun, Puerto Rico.

A gust of wind off the Caribbean apparently caused the founder and patriarch of the world-famed "Great Wallendas" aerial troupe to lose his balance. As hundreds of onlookers watched in horror, Mr. Wallenda crouched on the wire in an effort to regain control. He put one hand on the wire and held his balancing pole with the other.

Then, still clutching the pole, he plummeted an estimated 120 feet onto the driveway of the Condado Holiday Inn Hotel. His head struck a parked taxicab.

Five minutes later he was pronounced dead at Presbyterian Hospital in San Juan.

"You know, you have to face reality," Mr. Wallenda said in an interview last month, shortly before the broadcast of the television movie "The Great Wallendas." "You can go on an airplane and die, after all. We all want to achieve - something."

The purpose of yesterday's stunt was to walk a tightrope between the towers of the Condado and the Flamboyan Hotel to publicize the Pan American Circus, in which Mr. Wallenda and his granddaughter, Rietta, were appearing in San Juan.

It ended a career that began more than 50 years ago. It was a career in which Mr. Wallenda and his family thrilled millions with their high-wire derring-do and their scorn for the use of safety nets.

And it was a career in which Mr. Wallenda became famous for his dedication to the proposition that the show must go on whatever the cost. The cost included the death of three members of the family in stunts in which Mr. Wallenda himself was taking part, and the paralysis from the waist down of his son, Mario.

In the most tragic of the accidents, the troupe's "seven-person pyramid" collapsed 35 feet above the concrete floor of the Michigan State Fairgrounds Coliseum in Detroit on Jan. 30, 1962. Two were killed and three others, including Mr. Wallenda, were injured. The mishap was reenacted in the recent television movie.

In Sarasota, Fla., where Mr. Wallenda lived with many other circus people, his nephew, Gunther Wallenda, announced yesterday that "the act will continue, even without Karl."

In San Juan, James B. Harrington, manager of the Pan American Circus, said Mr. Wallenda appeared to be unconcerned about the wind posing a special hazard in his "walk."

"He thought it was fine," Harrington said . "He tested and installed the wire himself."

Gary Williams, a San Juan newspaper photographer, said Mr. Wallenda was leaning into the wind as he walked across th high wire.

His balace pole was going up and down," Williams said. "One of the people who work with him in the act was watching him from the roof. He yelled, 'Sit down, sit down!' Wallenda sat, but he missed the wire and went down.

"The people who work with Wallenda in the act ran around in a panic, screaming, 'Oh, my God, Oh, my God!" Williams added. "Everybody was hysterical. People wre fainting, collapsing on the ground."

Victor Abboud, an accountant from Montreal who saw the fall, said, "I saw him go down on his knees on the wire and I thought he was kneeling to rest. But then I saw he was shaking. The wind blew him off and he went all the way down, head first."

In Sarasota, Sandy Wallenda, the aerialist's niece, said, "I guess that's where he would have wanted to go. He would have kept walking all his life. He couldn't stop."

In New York, Kenneth Fold, producer of the Ringling Bros, Barnum and Bailey Circus, with which the Wallenda troupe starred for many years, expressed similar thoughts.

"If anyone could choose the way they had to go, I would say that would have been Karl's way," Feld said. "Karl was a talent and a performer. He had a way of getting an audience. He was a great inspiration to my young performers thorughout the years."

Mr. Wallenda was born in Hamburg, Germany, into a family of circus performers. He began appearing as a clown in circuses at the age of 5, and later learned tumbling. He was 16 before he began to practice on the high wire.

"I said to my brother - who was four years older than me - I said, 'Herman, you want to learn high wire? Good! Then I'm the boss!" Mr. Wallenda said in an interview last month.

Having learned tightrope walking, they came to the United States in the 1920s. "The great Wallendas" - sometimes called "The Flying Wallendas," a name that Mr. Wallenda disliked because it connoted trapeze work - were among the acts to open the Radio City Music Hall in New York in 1928.

Through the 1930s and until the late 1940s, the Wallendas performed with the Ringling Bros., Barnum and Bailey Circus. Mr. Wallenda started his own show in the late 1940s, went broke, and returned to the circus.

The failure of the "seven-person pyramid" in Detroit in 1962 was the troupe's first serious accident. The trick called for four men to stand on the high wire. They were linked by shoulder bars. Two others stood on the shoulder bars. These two were linked by another bar. A woman sat on a chair balanced on that bar.

Dieter Schepp, the husband of Mr. Wallenda's niece, Christiana, suddenly yelled, "i can't heold on any longer.

Shepp, who was making his first appearance, was killed. So was Richard Faughn, the son of the brother of Mr. Wallenda's first wife. Mr. Wallendas first wife. Mr. Wallenda's adopted son, Mario, was paralyzed in the fall. Mr. Wallenda himself manged to hand on to the wire with his knees. He caught and held onto Christiana Schepp. Herman Wallenda also managed to grab the wire. Herman's son, Gunter, remained standing on the wire.

A year later, Mr. Wallenda's sister-in-law, Yetta Grotofent, was killed in Omaha, Neb., while appearing in a balancing pole act.

In 1972, Mr. Wallenda's son-in-law, Richard Guzman, was killed in Wheeling, W.Va., when he touched a high-voltage electrical wire and fell from a tower toward which Mr. Wallenda was walking on a high wire.

Among the solo appearances Mr. Wallenda made were walks across the Veteran's Stadium in Philadelphia, a walk across Tallulah Falls in Georgia in 1970, a walk across Clapham Common in London, in the middle of which he did a somersault 70 feet above the ground, and a walk between the Eden Roc and Fontainebleau hotels in Miami Beach in 1977. The last feat was shown on national television.

After the Wheeling accident in which Richard Guzman died, Mr. Wallenda said, "Our life is show business. Without show buiness we don't survive and we have to exist."

Mr. Wallenda's survivors include his wife, Helen, who retired from the troupe in 1960, and who was with him in Puerto Rico at the time of his death.