A qualitative study was performed to: investigate the process that leads couples to decide for vasectomy; characterize the gender relations involved in this process; and identify sources of information on vasectomy. Semi-structured interviews were conducted with 20 couples who had requested vasectomy at the outpatient clinic of the Center for Integrated Women's Health Care, State University in Campinas, São Paulo, Brazil. A structured form was used to collect social, economic, and demographic data. The content analysis technique was used for data analysis. The majority of couples opted for vasectomy as a last resort after attempting numerous other contraceptive methods, not always successfully. The emerging gender relations showed fluctuation between: (1) a more rigid, quasi-patriarchal model characterized by male predominance in the family's decision-making and (2) a more ambiguous model in relation to reproductive decisions, whereby women assumed responsibility for contraception until the situation became untenable, at which point men faced up to the unavoidable necessity of sterilization. At this point the male partners felt they should collaborate.