This article analyzes policies that affected the availability of praziquantel, the drug of choice for schistosomiasis. The study examines how interactions among four actors (pharmaceutical producers, international agencies, non-governmental agencies, and national governments) affected praziquantel availability in poor countries. It also examines trends in praziquantel prices over time in different markets. This analysis demonstrates that the discovery of an effective new drug does not necessarily result in access to the drug for disease sufferers--especially if those sufferers are poor people in poor countries. The article proposes measures to improve international systems for making new drugs available in poor countries.