Trypanosoma cruzi and Leishmania are closely related intracellular protozoan parasites that cause serious diseases throughout the world. In the first part of this lecture, I will present background material on the biology of Trypanosoma cruzi and the history of its discovery as an important agent of human disease in Latin America. I will also discuss the main characteristics of the disease, and the current efforts to stop human transmission. See more at http://www.ibioseminars.org