The International Core of the HIV Center for Clinical and Behavioral Studies is a resource for the development of international research initiatives by HIV Center investigators working in collaboration with local institutions and investigators in Brazil, Namibia and South Africa. The Core also develops comparative analyses of key theoretical and topical issues, particularly in the areas of sexuality and gender relevant to the global response to HIV, in order to both contribute to the development of scientific knowledge and to inform local and international policy formation. Collaborative projects in southern Africa include the AIDS International Training and Research Program to develop epidemiological training and research, training programs for mental health providers, and a study of gender norms in heterosexual dating among young adults. Collaborative research in Brazil includes studies of treatment adherence, social mobilization in response to AIDS, HIV prevention among the mentally ill, and a study of AIDS- related policy formation.