Since many evaluations of HIV (human immunodeficiency virus) prevention programmes do not include data on costs, a preliminary analysis of the costs and outputs of a sample of HIV prevention projects was attempted. Case studies, representing six broad HIV prevention strategies in developing countries with differing levels of per capita gross domestic product, were sought on the basis of availability of data and potential generalizability. The six prevention strategies studied were mass media campaigns, peer education programmes, sexually transmitted disease treatment, condom social marketing, safe blood provision, and needle exchange/bleach provision programmes. Financial cost data were abstracted from published studies or were obtained directly from project coordinators. Although estimates of cost-effectiveness were not made, calculations of the relative cost per common process measure of output were compared. Condom distribution costs ranged from US$ 0.02 to 0.70 per condom distributed, and costs of strategies involving personal educational input ranged from US$ 0.15 to 12.59 per contact.