Among 683 snakes from several localities of Brazil, 16 (2,4%) presented in their blood (in mature or immature red cells) Toddia or Pirhemocyton. We named provisorily Toddia the parasites found in Bothrops moojeni, B. pradoi, B. jararaca and Chironius flavolineatus and Pirhemocyton those found in B. alternatus; we give the first reference in these hosts. These parasites were comparatively studied in view to establish the range of their relationship. With Toddia from B. moojeni we attempted nucleic acids by cytochemical methods and we found only DNA. The most affinities among the parasite that we have studied remained on the characters of the chromatic corpuscles and the cellular changes determined by them; we observed almost total identity among the parasites of same species of snakes. We observed the coexistence of globoides, crystalloids and intermediate forms between them allied to the parasites of B. pradoi and B. alternatus; in C. flavolineatus we found younder cristals, scarce intermediary forms between these and globoids. Affinities between Toddia and Pirhemocyton including the type of inclusion oppose to the original descriptions, turning doubtfull this generic separation. We also discuss the basis of the establishment of the species and the possible viral nature of these parasites.