The genetic distance calculations for 45 Bolivian stocks of Trypanosoma cruzi show the lack of continuum among them and allow to distinguish two main groups, which origin is perhaps a passed speciation. The presence of some heterogeneity within each group leads us to propose a temporary terminology: each isozymic variant is called "zymostrain" without prejudging its medical or taxonomic importance. The relationships between biochemical Taxonomy and medical data are discussed. The taxonomic value of the different isoenzymes is examined. The possible immunogenic properties of some of them (particularly Glutamate deshydrogenase) is discussed.