Zero Mostel, 62, the bearlike, brilliantly expressive comic actor whose profoundly moving perfomance in "Fiddler on the Roof" helped make him one of the foremost figures on the American stage, died last night in Philadelphia.

Mr. Mostel had been appearing in a new play, "The Merchant,"" which was being prepared for a Broadway perfomances because of a viral illness, according to a spokeswoman for Thomas Jefferson University Hospital, where he died. Death was attributed to cardiac failure.

As a verbal comedian, Mr. Mostel was a man of volcanic volubility, constantly erupting into wild, wry, riotous commentary on the world around him.

A skilled pantomimist as well, Mr. Mostel possessd remarkable grace despite his great girth, and made the fullest expressive use of his huge dark eyes, shaggy brows and hulking frame. He was a master of the meaningful gesture.

At his best, he fused wit and image to become a performer recognized by many as a true comic genius.

Admires saw in him an heir to Chaplin, an equal to Groucho Marx, a man who raised comedy to the level of art and used it to illustrate and illuminate the joys and ironies of the human condition.

An irrepressibly zany, madcap. Some of early satirical rountines figure, Mr. Mostel himself did not encourage serious srutiny of his own style and character.

"Don't include so many facts," he once warned an interviewer. "I don't want my character to suffer from an excess of rationaluty."

When an interviewer, seeking the essence of Mr. Mostel's art, suggested: "You really like people, don't you?" the response was. "Why not?" What should I like, tin cans?"

Nevethless, Mr. Mostel could be serious about humor, as when he lectured at Harvard's Loeb Drama Center in 1962, and said: "The freedom of any society varies in proportion with the volume of its laughter."

Mr. Mostel was born into an Orthodox Jewish family in the Brownsville section of Brooklyn, Feb. 28, 1915, and he grew up in Connecticut, the Bronx and the lower East Side of Manhattan.

His true name was Samuel Joel Mostel. For reasons never clearly explained, childhoold schoolmates gave him the nickname zero.

As a young man, his passion was for painting and, in 1935, he graduated from the City College of New York with a degree in art. In later years, he was fond of desscribing himself as "a painter who acts for a living."

After college, he roamed the country for a time, working in factories and on docks, then got an artist's post in a WPA program and painted. To keep himself in brushes and canvas, he began doing conic routines at parties, for about $5 a night, were topical commentaries, fueled by the social conscience he developed while working at alboring jobs.

He also did vivid, offbeat impressions. "He used to imitate wall paper, a percolator, all sorts of abstract things," a friend recalled. "You could SEE the steam coming from the top of his head."

After being spotted at a party, he won a $40-a-week nightclub job, and scored a quick success with his comic expressiveness. Radio, stage and Hollywood work soon followed. He made about a dozen films in the 1940s and 1950s, starting with "DuBarry Was a Lady" in 1942.

He sometimes played villains and other straight dramatic parts, enhacing a reputation for versatility.

In 1955, his career seemed headed for trouble. He appeared before the House Un-American Activities Committee for questioning about possible Communist Party membership and associations. He invoked the Fifth Amendment.

He was blacklisted and could get no film work for years. Recently, he wryly suggested that might have been a lucky break: "I would have wound up always playing the guy who didn't get the girl."

In recent years, he returned to the movies, appearing in several films, including "The Producers" and last year's "The Front," a drama about the blacklist victims.

For about three years after the House Committee apearance, his only work was on Broadway and that was sporadic. He helped support himself by painting. The resurrection of his acting career came in 1958 when he played Leopold Bloom in an off-Broadway production of "Ulysses in Nightown," based on a segment of James Joyce's Ulysses.

He won the Oble award for the season's best off-Broadway actor, then went on to win lavish praise in Ionesco's "Rhinoceros" in 1961. The performance won hin the first of hos three Tony awards for best Broadway actor of the year.

The second came for "A Funny Thing Happened on The Way to the Forum" (1962), and the third was for "Fiddler on the Roof."

His portrayal of the play's l eading character, Tevye, an impoverished, long-suffering dairyman who seemed to have an inimate, informal relationship with God, was widely acclaimed as a triumph.

Although a star and a celebrity, Mr. Mostel tried not to act like one, attempting to avoid public relations men, image-makers and crowds of admiring hnagers-on that sometimes surround the famous.

His professed aim was to play the roles he wanted to play and sy the things he wanted to say. In saying things about himself, the tone was often self-mocking.

Success, he said, "didn't go to my head. It went to my waistline."

Survivors include his wife, Kathrynand two sons.