Working with ten strains of T. cruzi isolated from human cases of Chagas' Diseaze, in standard condictions, the author made a morpho-biometric and biologic studies of the strains to verify the possibiW.y of existence of relationship between their characterislics. Studies on the biometric data, pathogenicity to baby mices, infectivity to triatomines and cultivation in artificial media (Warren and N NN) mere made. The results showed no existence of relationship between the morphology and the pathogenicity of the several strains studied.