Director Mark Robson had a very combative relationship with all his actresses, particularly singling out Sharon Tate for his harsh treatment. Patty Duke hated working with him, and years later, after his death, still called him "a mean son of a bitch".
The novel and, by extension, this film adaptation are loosely based on novelist Jacqueline Susann's experience as an actress from the late 1930s to the late 1950s. When her acting career never took off, she settled for her second career of choice - writing novels.
Some ads for the film featured photos of the female leads, along with taglines about each individual character and her pill color of preference. (e.g., "This is so-and-so; she took the red pills.") Unfortunately, the ad department hadn't paid much attention to the movie, because the same approach was taken with Susan Hayward's character Helen Lawson - the only lead female character who didn't take pills and, in fact, was quite vocal in her dislike of recreational pill-popping.
Judy Garland originally was cast in the role of Helen Lawson. She was fired because of her drinking and behavior and was replaced by Susan Hayward. Other actresses considered as replacements were Tammy Grimes and Bette Davis.
The novel begins during a heat wave in New York City at the end of WWII, whereas the film opens in the middle of winter with lots of snow. This occurred because the producers were anxious to get the film into production and didn't want to wait for the warmer weather; a fact which infuriated the book's author Jacqueline Susann. The film version also was updated so that instead of taking place from 1945 through the 1950s, the storyline ran from the mid- to late-1960s.