This work provides evidence that nicotine (1 x 10(-5) M) can cause changes in the intracellular calcium concentration of Trypanosoma cruzi epimastigotes, which can be blocked by Lu-bungarotoxin but not by atropine. Moreover, parasite membranes also bind such nicotinic acetylcholine receptor antagonist as well as agonists such as carbamylcholine (IC50: 7.6 x 10(-7) M) and nicotine (IC50: 1 x 10(-7) M), Results suggest that there is a molecular species in the surface of the parasite able to bind nicotinic ligands; therefore, nicotine interaction could lead to the activation of the mechanisms involved in intracellular calcium concentration increase in the parasite,