Three strains of Trypanosoma cruzi, used previously as prototypes for a classification based on the host-parasite relationships! as well as several stocks isolated from different geographical areas in Brazil, were submitted to lsoenzymic analysis. Their isoenzyme patterns revealed a clear correlation with the biological data. The patterns obtained with the enzymes PGM, GPI, ASAT and ALAT permitted discrimination between each of the described types. Only one type was found in each geographical area studied, indicating a possible relationship between regional patterns and clinical presentation of Chagas’ disease.