Trypanosoma cruzi, the etiological agent of Chagas disease, is an adequate model for studies on the evolution of signal transduction pathways. These pathways involve molecular entities such as membrane receptors, transduction G proteins, protein kinases and second messengers (Ca 2 + , cyclic AMP, cyclic GMP, nitric oxide). In this article, Mirtha M. Flawia, Maria T. Tellez-Inon and Hector N. Torres describe the studies performed on T. cruzi transduction pathways and their role in the control of metacyclogenesis and cell motility.