This paper addresses the historical context, both ancient and modern, of the injunction prohibiting sexual relationships with patients. Reference is made to the increasing knowledge of factors predisposing to such breaches of ethical conduct and to the common dangers and consequences of sexual relationships with patients. Such research findings demonstrate adequate cause for the application of the injunction in all of the health care professions. The modern social context of liberal humanism and feminism, along with the recognised analogy with child sexual abuse, are considered as influences in the current resurgence of interest in the injunction itself.