BACKGROUND: As HIV spreads through many countries in Asia and the Pacific, women of reproductive age are becoming infected and we can expect increasing numbers of infants to be infected. Rapid advances in knowledge about mother to child transmission (MTCT), new findings from intervention studies, recognition of complex ethical implications, and changing attitudes and behaviours combine to create uncertainty for policy makers. OBJECTIVE: Policy makers need sound advice but MTCT and its prevention are complicated topics. We aim to provide an overview of MTCT of HIV and suggest some key points to consider in the allocation of resources. STUDY DESIGN: This is a policy analysis based on review of the literature, consultation with policy makers and researchers, and observations in the context of projects in developing countries. RESULTS: The risk of MTCT is between 15 and 40%, but the use of antiretroviral prophylaxis, elective caesarean section, and replacement of breastfeeding can reduce this to less than 4%. But most infected women in developing countries are unaware that they are HIV-infected and do not yet have access to these ‘test-dependent’ interventions (interventions based on testing for HIV infection). Population-based strategies that address known influences on the risk of MTCT can be implemented with benefits for the health of both men and women. The test-dependent interventions can have adverse effects as well as benefits, careful preparation is necessary before they are introduced in resource poor settings. The public health impact of test-dependent interventions is limited by difficulties in achieving wide coverage and because they miss women who become infected late in pregnancy or during lactation who have the highest risk of MTCT. CONCLUSIONS: We argue for a broad response to the problems raised by MTCT of HIV that includes gathering information to inform the introduction of strategies that do not depend on testing for HIV infection as well as the test-dependent interventions, community education that reaches men as well as women; strengthening of reproductive health services; and mobilising communities to care for infected women, their families, and orphans.