Changes in the dynamic of expression of polypeptides following the differentiation from infective trypomastigotes to multiplicative amastigote forms of Trypanosoma cruzi were mapped by two-dimensional gel electrophoresis and quantitatively analyzed by laser densitometry. Following the differentiation from trypomastigotes to amastigotes the expression of the polypeptides 212, 183, 176, 149, 50-55, 43, 39, 34 and 28 kDa is turned off in multiplicative amastigotes, whereas the expression of the polypeptides 80, 66 (p.Is. 6.75-7.50), 42 and 38 kDa is turned on. After complete differentiation from trypomastigotes to amastigotes the expression of the polypeptides 43, 42, 33, 32, 29 and 23 kDa is up-regulated in amastigotes, whereas the expression of the acidic polypeptides 66 (p.Is. 6.27-6.64), 45-48 and 41-43 kDa is down-regulated.