Insurance worker C.C. Baxter (Jack Lemmon) lends his Upper West Side apartment to company bosses to use for extramarital affairs. When his manager Mr. Sheldrake (Fred MacMurray) begins using Baxter's apartment in exchange for promoting him, Baxter is disappointed to learn that Sheldrake's mistress is Fran Kubelik (Shirley MacLaine), the elevator girl at work whom Baxter is interested in himself. Soon Baxter must decide between the girl he loves and the advancement of his career.

Renowned dressmaker Reynolds Woodcock and his sister Cyril are at the center of British fashion in 1950s London -- dressing royalty, movie stars, heiresses, socialites and debutantes. Women come and go in Woodcock's life, providing the confirmed bachelor with inspiration and companionship. His carefully tailored existence soon gets disrupted by Alma, a young and strong-willed woman who becomes his muse and lover.

Upper-crust executive Louis Winthorpe III (Dan Aykroyd) and down-and-out hustler Billy Ray Valentine (Eddie Murphy) are the subjects of a bet by successful brokers Mortimer (Don Ameche) and Randolph Duke (Ralph Bellamy). An employee of the Dukes, Winthorpe is framed by the brothers for a crime he didn't commit, with the siblings then installing the street-smart Valentine in his position. When Winthorpe and Valentine uncover the scheme, they set out to turn the tables on the Dukes.

In 1977, college graduates Harry Burns (Billy Crystal) and Sally Albright (Meg Ryan) share a contentious car ride from Chicago to New York, during which they argue about whether men and women can ever truly be strictly platonic friends. Ten years later, Harry and Sally meet again at a bookstore, and in the company of their respective best friends, Jess (Bruno Kirby) and Marie (Carrie Fisher), attempt to stay friends without sex becoming an issue between them.