This paper highlights extensive variation in Muslim interpretations of sexual life by discussing views on and the management of sexual life in one specific locality (Zanzibar) where sexuality is perceived to be an ambivalent force, dangerous and creative at the same time. Efforts to channel sexuality in Zanzibar are directed at enhancing the positive side of sexuality and at controlling its negative force through sex education, gender segregation, the control of the body fluids and secrecy in the management of non-marital affairs. The paper discusses the positive and negative outcomes of sex and links them to the perceived ambivalent qualities of the body fluids involved, illustrating some of the strategies used to control sexual desire. The increasing spread of HIV and the influence of more essentialist trends in Zanzibari Islam draw attention to the capacity for dynamic adaptation of perceptions and practices.