Chagas disease occurs throughout Mexico and central and southern America and continues to pose a serious threat to health in many countries of the region. People infected with the trypanosome parasite may suffer cardiac, gastrointestinal, or neurological damage, although disease manifestations vary widely from one endemic area to another. In the past decade, control programmes in several endemic countries have proved remarkably successful; interruption of disease transmission has been achieved in some and is imminent in others, leading to a substantial reduction in the incidence of Chagas disease in Latin America. However, 8-9 million people in Mexico and the Andean and central American countries are infected with the parasite and 25 million remain at risk, emphasizing the need to sustain and extend control strategies. This report of a WHO Expert Committee reviews current knowledge of Chagas disease and its pathogenesis, discusses the causative parasite, the triatomine vectors, and the natural reservoirs of infection, and considers the epidemiology and incidence trends of the disease. Prevention and control strategies are described, as are the various formal initiatives for interruption of disease transmission. The report concludes by identifying priorities for research and offering guidance for the planning, implementation, and strengthening of national control programmes.