The Islamic Republic of Iran arguably has one of the most successful family planning programs in the developing world. This success is all the more interesting for advocates of population programs because the political leaders of the Islamic regime were once strongly opposed to family planning. Indeed, after gaining power following the 1979 revolution, they were responsible for dismantling Iran's relatively new family planning program and introducing pronatalist policies. This article provides an account of the different phases of the population policy in Iran and examines the diverse elements that led politico-religious leaders to revise their views about fertility control and to participate in creating a workable family planning program. The complex formal and informal strategies that the political experts, the media, the religious authorities, and the government of the Islamic Republic adopted in order to achieve this about-face are described. The analysis is based on data collected by the first author during anthropological field research in 1993-96, by means of informal interviews with officials, with medical personnel, with family planning clients, and with religious leaders.