The development and marketing of medicines needed specifically to combat diseases of the developing world are commercially unattractive because the populations concerned are among the poorest on earth. Partnerships which bring together pharmaceutical companies, academics, not-for-profit organizations, philanthropists, governmental and inter-governmental agencies are an increasingly popular solution. These partnerships result in a complementarity of skills and resources that can accelerate the development and delivery of new medicines to those in need. Over the last 10 years or so, these public-private partnerships (PPPs) have grown significantly in number and diversity. However, they tend to cluster into two main groups: those dealing with product development (PD PPPs), and those concerned with improving the access of new medicines to target populations (Access PPPs). The Initiative on Public-Private Partnerships for Health was set up four years ago to monitor the performance of these new partnerships. After a series of studies of Access PPPs, it concluded that they provide significant benefits with very few side effects, particularly in the case of tropical diseases.