Douglas Fairbanks Jr., 90, the son of Hollywood royalty whose debonair presence in about 80 films as cads and good-natured gadabouts gave way in the 1940s to a second career as a television producer and social lion, died May 7 at a hospital in New York. The cause of his death was not disclosed.

Mr. Fairbanks may have inherited his screen-legend father's broad, rakish smile and trim figure, but he never adopted as a trademark the indefatigable athleticism with which the elder Fairbanks so electrified audiences in silent film classics.

The younger Fairbanks had a more sophisticated energy that enlivened scores of workmanlike dramas and light comedies of the early 1930s. With clipped, almost British voice inflections, a hairline mustache and an expression of gentle world-weariness, he usually played mouthy men about town, sly newspaper columnists and adventure-seeking flaming youths.

Some of his best-known films from that period include the "The Narrow Corner," a 1933 drama based on a W. Somerset Maugham novel, and Howard Hawks' 1930 movie about World War I flying aces, "The Dawn Patrol." He demonstrated delightful comic timing in William Wellman's "Love Is a Racket" in 1932, and starred with Ginger Rogers in "Having Wonderful Time" in 1938.

In the 1930s he also had appeared in such films as "Little Caesar," "The Prisoner of Zenda" and "Gunga Din." He also had the male lead in the 1934 period piece "Catherine the Great," playing Grand Duke Peter III of Russia.

His last film was "Ghost Story," a 1981 horror tale with Fred Astaire. The vast majority of his movies were made before 1940, at which point Mr. Fairbanks began devoting his time to World War II efforts.

Dating to the late 1930s, the American government had enlisted the Anglophilic Mr. Fairbanks to facilitate a visit to the United States by King George VI and Queen Elizabeth. From 1939 to 1941, he was a member of the British War Relief Association and quickly became a prominent figure aligned with other relief efforts. In 1941, President Franklin D. Roosevelt appointed him a special envoy to several South and Central American counties.

He was called to active Navy duty in 1941 and rose to commander during his five-year service. He saw combat in Europe and the Mediterranean. His assignments included serving under British Adm. Lord Louis Mountbatten in a commando operation.

Mr. Fairbanks, whose military awards included the Silver Star and Legion of Merit, retired from the reserve as a captain in 1954. In 1949, King George VI of England gave Mr. Fairbanks an honorary knighthood.

Through his wartime connection to Mountbatten, Mr. Fairbanks entered high British social circles.

In 1953, press accounts told of a historic dinner he gave in honor of Queen Elizabeth II and other members of the royal family.

"It was the first recorded time that a British monarch has stepped outside court circles to dine at a private house, and it set the seal on the social career which the Fairbankses have been building in postwar London," according to one dispatch.

Another report said: "Entree into the Fairbankses' home is a hundred times more difficult that getting a ticket for the coronation."

After World War II, he formed a new production company, but his acting career did not quicken despite a few well-received films. Perhaps his best-known postwar motion picture was 1947's "Sinbad the Sailor," a swashbuckling tale that was a winking throwback to his father's oeuvre.

He turned to television, and from 1953 to 1957, he hosted a half-hour anthology series called "Douglas Fairbanks Jr., Presents." He acted in and starred in about one-fourth of the programs, which were made in England and broadcast to the United States.

He continued to act in stage plays, even into his later years. "I do one play a year, and that's about it," Mr. Fairbanks told The Washington Post in 1982 when he was honorary CARE chairman. "Like any good gambler I quit while I was ahead. . . . I'd much rather have people ask me why I stopped acting instead of 'Why don't you stop acting?' "

He several appearances on the Washington stage included starring in two comedies at the Kennedy Center, Samuel Taylor's "The Pleasure of His Company" in 1972 and Noel Coward's "Present Laughter" in 1975.

Douglas Elton Fairbanks Jr. was born in New York to Douglas Fairbanks (whose real name was Douglas Ulman) and the actress Anna Beth Sully. His parents divorced when he was 9, and he lived with his mother. His father, from whom he was estranged for decades, later married "America's Sweetheart," the actress Mary Pickford.

Mr. Fairbanks spent the early 1920s studying sculpture and architecture but decided to try his hand at films. In 1923, at his father's film peak, the younger Mr. Fairbanks made his movie debut in the comedy "Stephen Steps Out." But Mr. Fairbanks, who once said that his father "had no more paternal feelings than a tiger in the jungle for his cub," broke his own $2,000-a-week film contract that year after learning he only got it because of his father's fame.

After doing stage acting, he returned to films, and by the late 1920s, he was being promoted as a star in his own right. In 1928, he and appeared opposite Greta Garbo in "A Woman of Affairs" and played the lead in an early Frank Capra film, "The Power of the Press."

Mr. Fairbanks postwar career included lecturing in diplomatic, cultural and business circles about the benefits of trans-Atlantic ties. As a private citizen he performed temporary diplomatic government assignments.

In subsequent decades, he was a director and consultant for international firms and a member of the executive committee of the Royal Shakespeare Theatre in England. He also painted and sculpted and wrote the first volume of his memoirs, published as "The Salad Days" in 1988.

His first marriage, to actress Joan Crawford, ended in divorce. His second wife, the former Mary Lee Hartford, the ex-wife of A&P supermarket heir Huntington Hartford, died in 1988.

Survivors include his wife, the former Vera Shelton. He had three daughters by his second wife.