MORE SUCCESSFULLY than most playwrights of his generation, Paddy Chayefsky practiced the triangular trade of creating dramas for a mixture of motion picture, stage and television audiences. The Chayefsky protagonist -- male, middle-aged and mordant -- displayed at least one trademark of sorts from that early gem of a play, "Marty," which brought him fame, to the manic desperation of such later works as "Hospital" and "Network": he seethed memorably. Mr. Chayefsky's characters could be relied upon to rail eloquently at their distinctively personal sense of entrapment. In the older plays, the complaints were mild and often humorous. As Mr. Chayefsky aged, however, his anger grew at the social conditions that generated the "dehumanization" (a favorite word increasingly) that he came to lament within American life.

He was born Sidney Chayefsky in 1923. In every sense, he was a New Yorker -- by birth and by education, by the scene of his writing (often) and by his residence until death. Mr. Chayefsky's generation was that of World War II, from which he emerged with an Army-earned Purple Heart, the nickname "Paddy" (which stuck) and -- unlike many of his contemporaries -- with an interest in writing not the Great American Novel but a comparably important radio or television play.

His reputation as a dramatic craftsman emerged by the mid-1950s through a flurry of superb plays -- written first for television but later produced in stage or film versions -- including "Middle of the Night," "The Bachelor Party," "The Catered Affair," and -- most popular of all -- "Marty." The poignant tale of a lonely Bronx butcher who fell in love with a schoolteacher displayed Mr. Chayefsky's gift for dialogue along with an almost painful degree of compassion for his main characters. The compassion seemed to erode in subsequent years as the playwright's view of American realities darkened.

Although Mr. Chayefsky continued to turn out powerful and disturbing dramatizations -- most adroitly so in the motion pictures "Hospital" and "Network" -- his choice of theme and personage reflected an artistic temper increasingly embittered at the loss of gentleness within the cityscape he had staked out as his own. If Paddy Chayefsky had written nothing else in recent years, these two film portrayals of the tenuous survival of decent behavior in two oddly comparable urban snakepits -- the wards of a manic metropolitan hospital and the Machiavellian skyways of a television network news operation -- have ensured him an admiring posthumous audience.