This report provides a review and analysis of the research landscape for three diseases - Chagas disease, human African trypanosomiasis and leishmaniasis - that disproportionately afflict poor and remote populations with limited access to health services. It represents the work of the disease reference group on Chagas Disease, Human African Trypanosomiasis and Leishmaniasis (DRG3) which was established to identify key research priorities through review of research evidence and input from stakeholders' consultations. The diseases, which are caused by related protozoan parasites, are described in terms of their epidemiology and diseases burden, clinical forms and pathogenesis, HIV coinfection, diagnosis, drugs and drug resistance, vaccines, vector control, and health-care interventions. Priority areas for research are identified based on criteria such as public health relevance, benefit and impact on poor populations and equity, and feasibility. The priorities are found in the areas of diagnostics, drugs, vector control, asymptomatic infection, economic analysis of treatment and vector control methods, and in some specific issues such as surveillance methods or transmission-blocking vaccines for particular diseases. This report will be useful to researchers, policy and decision-makers, funding bodies, implementation organizations, and civil society. This is one of ten disease and thematic reference group reports that have come out of the TDR Think Tank, all of which have contributed to the development of the Global Report for Research on Infectious Diseases of Poverty, available at: www.who.int/tdr/stewardship/global_report/en/index.html.