The huge success of The Dirty Dozen (1967) the year before had given director Robert Aldrich the opportunity to set up Aldrich & Associates. This gave him the freedom to pursue more challenging and stimulating subject matter, of which "The Killing of Sister George" was the first example.
The original Broadway production of "The Killing of Sister George" by Frank Marcus opened at the Belasco Theater in New York on October 5, 1966, ran for 205 performances and was nominated for the 1967 Tony Award for the Best Play. Beryl Reid won the 1967 Tony Award for Best Actress in a Play and recreated her role in the movie version.
The scene in the lesbian bar was filmed in a real one - the Gateways Club in London. This generated a lot of controversy, as audiences weren't used to seeing lesbians interacting so openly with each other.
When first submitted in 1969 UK censor John Trevelyan refused to grant a certificate unless the seduction scene was toned down and urged all 600 local authorities to boycott the film. 12 councils, including the GLC, overrode him and showed the film with their own X certificate. After heated discussions with the distributor the kissing scene was slightly reduced and Trevelyan eventually passed the movie. All video/DVD versions of the film are the original uncut one.