HOLLYWOOD, June 22--David O. Selznick, one of the leading producers in the motion picture industry, died of a coronary occlusion this afternoon at Mount Sinai Hospital. Mr. Selznick, who was 63 years old, was stricken in the office of his lawyer, Barry Brannen, in Beverly Hills, and was rushed to the hospital. His wife, Jennifer Jones, the actress, was with him at the time of the attack. Mr. Selznick, who produced "Gone With the Wind," the movies' biggest money-maker, and his wife had returned to their Beverly Hills home last week after spending three months in New York City. Mercurial, shrewd, self-confident and enormously gifted, David O. Selznick climbed to the pinnacle of power and success in Hollywood with films that are now classics and actors who are considered screen immortals. His films included "Intermezzo," "Rebecca," "David Copperfield," "Little Women," "The Prisoner of Zenda," "Dinner at Eight," "A Star Is Born," "Duel in the Sun," and the epic, "Gone With the Wind." He was instrumental in spurring the careers of such actors as Clark Gable, Vivien Leigh, Ingrid Bergman, Joseph Cotten, Gregory Peck, Katharine Hepburn, Joan Fontaine, Fred Astaire, Leslie Howard, Myrna Loy and his wife, Miss Jones. Mr. Selznick, a 6-foot 1-inch 200-pounder, moved quickly, spoke rapidly and worked tirelessly. He produced quality films with three trademarks: top stars, the finest writers and no expense spared. Even in the twilight of his career, he remained wide-eyed and even brash, although a trace of pessimism and melancholy became apparent in recent years. "Nothing in Hollywood is permanent," Mr. Selznick said in 1959 on a Hollywood set, as Tara, the mansion built for "Gone With the Wind," was being dismembered and shipped to Atlanta, Ga. "Once photographed, life here is ended. It is almost symbolic of Hollywood. Tara has no rooms inside. It was just a facade. So much of Hollywood is a facade." Mr. Selznick spoke in quick, staccato sentences. While working on a film, he virtually exhausted himself, laboring round-the-clock, seeking perfection to the minutest detail and stubbornly insisting on his own ideas. As a producer, Mr. Selznick was preoccupied with quality, and his perfectionism led him to many fights with directors. "Gone With the Wind" started with George Cukor directing. He was replaced by Victor Fleming. "A Farewell to Arms" saw a classic feud between Mr. Selznick and John Huston. "It was a case of one Alp and two Hannibals," said Mr. Huston after he had been replaced in Italy by Charles Vidor. "I asked for a violinist," Mr. Selznick shot back, "and, instead, in John, got a soloist." As one of Hollywood's most famous memo writers, Mr. Selznick dictated more than 1.5 million words of memos to two exhausted stenographers during the filming of "Gone With the Wind." At one point, he sent a message to Vivien Leigh that weighed half a pound and took the actress 10 days to reply to. Mr. Selznick was born in Pittsburgh, on May 10, 1902, the son of Lewis J. Selznick, a Russian immigrant who had earned and lost a fortune in the movie business. With unbounded confidence in the abilities of his two sons, Myron and David, the elder Selznick spared little expense in rearing them as prodigals. Myron, who later became a Hollywood agent, was given an allowance of $1,100 a week at the age of 21. The younger, David was given $300 a week at 18. David Selznick attended public and private schools and, for a brief period, Columbia University. He developed an interest in filmmaking in his early teens. The Selznick family fortune was swept away in the stock market crash. L. J. (as he was called in Hollywood and New York) moved from a 22-room apartment on Park Avenue to three furnished rooms where Mrs. Selznick did the cooking. All the family's possessions, including Mrs. Selznick's jewels were sold. With zest and self-confidence, the younger Selznick got his first movie job by cajoling Harry Rapf of Metro-Goldwyn-Mayer into hiring him, nominally as a reader of scripts at $100 a week at a two-week trial. Mr. Rapf had initially protested. "Readers don't get that kind of money," he said. "I know they don't," Mr. Selznick retorted. "But I'll do more for you than read scripts. I'll help you fix them. I'll write titles. I'll do everything that has to be done to them." Mr. Rapf hired him. Within several weeks, Mr. Selznick's pay was doubled and he was given a permanent job. A few months later, his salary was increased to $300 and he was appointed Mr. Rapf's assistant on the production of the Tim McCoy Western films. Mr. Selznick next went to Paramount, offering himself on a similar trial arrangement. He received a $300 job and became an assistant to B. P. Schulberg, head of the studio, who had told him early: "You're the most arrogant young man I've ever known." In April, 1930, Mr. Selznick married Irene Mayer, Louis B. Mayer's younger daughter. Mr. Mayer, the head of M-G-M, was furious when the young Selznick courted his daughter. He even refused to speak to him at the wedding. Shortly afterward, however, when the young man walked away from his job at Paramount, Mr. Mayer did have a few words to say to his new son-in-law. "How dare you give up that contract," he yelled. "And you married to my daughter." Mr. Selznick left Paramount to make films on his own, becoming vice president, in charge of all production at R.K.O.-Radio. It was there that he started producing such quality films as "A Bill of Divorcement," to which he brought Katharine Hepburn and George Cukor, the director, to Hollywood; "The Animal Kingdom," with Ann Harding, and the famous "King Kong." After planning "Little Women," Mr. Selznick resigned from R.K.O. to return to his father-in-law's studio, M-G-M, as vice president and head of his own production unit. Mr. Selznick was greeted coolly by most of the executives there. Many felt that he was using his relationship with Mr. Mayer to get ahead. "The son-in-law also rises," became one of the gags around Hollywood at the time. In an incident related by Bosley Crowther, film critic for The New York Times, in "The Lion's Share," Mr. Selznick was treated so coldly by M-G-M executives that, at one point, he went home, threw himself on the bed and cried. His wife comforted him, "Let them yammer," she said. "You can still take the best that the studio has to work with. Serve your term--and make some films!" Mr. Selznick's early films at M-G-M included "Dinner at Eight," "Dancing Lady" and "Viva Villa." Freddy Bartholomew was discovered by the producer and made famous in "David Copperfield." In 1935, the producer left M-G-M to form an independent company. He was backed by Cornelius V. Whitney, John Hay Whitney; his brother Myron; Robert and Arthur Lehman, the bankers; John Hertz and Irving Thalberg and Norma Shearer (Mrs. Thalberg). Mr. Selznick did not invest any money but he owned a little more than half of the company. In the early summer of 1936, Mr. Selznick was busy with "The Garden of Allah," with Marlene Dietrich, when a wire reached him from Kay Brown, the New York story editor, urging him to buy film rights to a new Civil War novel. It was "Gone With the Wind," by Margaret Mitchell, an unknown in the literary world. At the time, the feeling in Hollywood was that the Civil War had been played out with "The Birth of a Nation." Mr. Selznick, however, was interested although he had misgivings about the problems of producing a novel of such length (1,037 pages). Finally the novel was purchased for $50,000. As winter came and the sales of the novel soared, the reading public, spurred by Mr. Selznick's publicity, became interested in the cast of the film. Tallulah Bankhead, Norma Shearer and Bette Davis were mentioned for the leading role of Scarlett O'Hara. So strong was the public interest that when Miss Shearer declined to play Scarlett, The New York Times regretted her decision in an editorial. Vivien Leigh, a hazel-eyed, brown-haired British actress, was finally chosen in almost typically dramatic fashion. In order to clear the studio's lot for the building of Tara, the movie plantation, a maze of old sets had to be removed. It was suggested that instead of tearing down the sets, they should be burned and used to represent the dramatic highlight of the film, the burning of Atlanta. Mr. Selznick agreed. While the cameras were shooting the scene, and as flames rose in the studio's night sky, the producer felt a tug on his sleeve. He turned and saw his brother, Myron, accompanied by a beautiful girl. "I want you to meet Scarlett O'Hara," Myron said dramatically. Mr. Selznick stared at Miss Leigh and promptly signed her for the role. The picture went before the cameras officially on Jan. 26, 1938. During the 22 weeks of shooting, Mr. Selznick's work habits became legend. He worked at times at three-day stretches without sleep, feeding himself Benzadrine and thyroid extract and playing poker and roulette to relax. His memos became more prolific. At one point Clark Gable, the film's Rhett Butler, was routed out of bed at 3 A.M. by a messenger who presented him with a document--a memo on the portrayal of the role. Mr. Gable and the others finally revolted and established a 9 P.M. curfew on memos. At the time, the film was the most expensive ($4,250,000) and one of the longest (3 hours and 45 minutes) ever produced. It has since grossed in excess of $50 million and has been reissued several times. In seeking Mr. Gable for the film, Mr. Selznick agreed to a financial arrangement with M-G-M, the star's studio, in which M-G-M put up half the production costs in return for a share in the film's profits. "I have never regretted it," Mr. Selznick once said. "I wouldn't have made the movie without Clark." At the peak of his career, Mr. Selznick was voted for 10 successive years as the No. 1 producer of box-office successes by motion-picture exhibitors of the country. Despite this, Mr. Selznick was notably unsuccessful, at times, in hiring top actors and producers. On receiving an overture from the producer, Nunnally Johnson wrote: "I should certainly like to work for you, although my understanding of it is that an assignment from you consists of three month's work and six months of recuperation." A Hollywood saying was, simply, "Selznick eats directors, writers and secretaries." Since 1948, Mr. Selznick had been generally inactive in Hollywood, and in recent years had been involved in European film distribution, the sale of his films to television and several stage plays. None of the stage plays came to fruition. In 1949 Mr. Selznick married Jennifer Jones, and he became involved in the production of most of her recent films. Miss Jones, who had been married to the late actor Robert Walker, had starred in several of Mr. Selznick's films, including, "Duel in the Sun," and "Since You Went Away." The producer and his wife lived in an elegantly rustic home on an estate atop a hill overlooking Beverly Hills. They also maintained an apartment at the Waldorf Towers in New York. "Very few people have mastered the art of enjoying their wealth," Mr. Selznick remarked several months ago. "I have mastered that art and therefore I spend my time enjoying myself." Mr. Selznick added that on some mornings he arose with the determination to make another movie, but by 2 P.M., after a few phone calls and the reading of a script, he had decided to forget about it and take a nap instead. Mr. Selznick's death yesterday came on the same day when the last of a series of essays on him appeared in The Hollywood Reporter, a trade paper. The essays were published as advertisements written and paid for by Russell Birdwell, his well-known press agent. In the last essay, the final words were: ". . .come home, D.O.S." Mr. Selznick is survived by his widow, two sons by his first marriage, Louis and Daniel, and a daughter, Mary, by his second wife. Irene Mayer Selznick is now a Broadway producer. She and the producer were divorced in 1948.