Membrane rafts are small and dynamic regions enriched in sphingolipids, cholesterol, ganglioside GM I and protein markers like flotillins, forming the flatter domains or caveolins, which are characterized as stable flask-shape invaginations. We explored whether membrane rafts participate in the entry of Trypanosoma cruzi's trypomastigotes into murine macrophages through transient depletion of macrophage membrane cholesterol with methyl-beta-cyclodextrin and treatment with filipin. These treatments led to a decrease in the trypornastigote invasion process. Macrophage pre incubated with increasing concentrations of cholera toxin B, that binds GM I, inhibited the adhesion and invasion of trypomastigote and amastigote forms. Immunofluorescence analysis demonstrated a colocalization of GM1, flotillin 1 and caveolin 1 in the T cruzi parasitophorous vacuole. Taken together these data suggest that membrane rafts, including caveolae, are involved in the process of T cruzi invasion of macrophages. (C) 2007 Elsevier Inc. All rights reserved.