This is the third and final Hammer adaptation of Robert Louis Stevenson's novella "Strange Case of Dr Jekyll and Mr Hyde". The previous two were The Ugly Duckling (1959) and Dr Jekyll & Sister Hyde (1971)
Christopher Lee (Paul Allen) would later play Dr. Charles Marlowe and Edward Blake, the renamed Dr. Jekyll and Mr. Hyde, in I, Monster (1971), another adaptation of Robert Louis Stevenson's 1886 novella "Strange Case of Dr. Jekyll and Mr. Hyde".
Oliver Reed (Bouncer) would later play the title characters in Dr. Heckyl and Mr. Hype (1980), another adaptation of Robert Louis Stevenson's 1886 novella "Strange Case of Dr. Jekyll and Mr. Hyde".