chromosomal DNA from a Paraguayan Trypanosoma cruzi isolate was extracted and sonicated. The fragments were cloned and some clones were size-selectd and sequenced. Two primer pairs TC22 and TC4 were synthesized and applied to other Paraguayan T. cruzi isolates and two Leishmania mexicana amazoniensis strains by the polymerase chain reaction. The specificity and sensitivity of these primers were correlated with TCZ primer pair synthesized by Moser et al. Remarkable differences were observed between the three primer pair which could be possibly explained by the fact that TCZ primers unlike TC22 and TC4 amplify a highly repettitive sequence of chromosomal T. cruzi DNA