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One on Top of the Other was produced wholly by an Italian company but was shot in and around San Francisco, CA and was originally released in Italy under the title Una sull'altra. Some modern sources also list the title as Perversion Story, but that May have been a re-release title. Although all contemporary sources, including the pressbook, list Movielab as providing the film's color, the onscreen credits list Technicolor. Director Lucio Fulci, who appears briefly in the film as the handwriting analyst, used frequent zooms, jump cuts and trick shots, such as upside-down aerial views, throughout the film. In addition, in the scene in which "Susan Dumurrier" is exhumed and tested, a five-way split screen shows several laboratory tests; and in the scene in which Susan hones her disguise as "Monica Weston," a five-way split screen shows Monica at multiple striptease jobs.
As noted in the Variety review, additional filming locations included the San Quentin Federal Penitentiary and Reno, NV. Modern sources state that the film was shot in 1969. The Box Office review adds that most of the dialogue for the American release was dubbed into English. In December 1971, an Hollywood Reporter news item noted that American distributor GGP Releasing was planning to hold the film's American premiere in San Francisco, but no date was specified. The picture went on to open in Los Angeles in February 1973.