Toddia, a genus created by França 1911 for an organism found in the erythrocytes of an anuran amphibian, has a particular structure and the problem of its viral relationship of protozoa nature is an important point which has recently been discussed. Attempt to resolve this problem must be made using ultrastructure and cytochemical studies. Our results have shown a Feulgen positive reaction and a Methyl-Green positive reaction for this organism, chiefly in the beginning of the infection. At the end of the infection the particles are greater than that in the beginning but the reactions above cited are generaly wakly positive or negative. We have also employed the Acridine orange method in the characterization of DNA and the results are positive too. Further histochemical studies are necessary to determine the true nature of the material observed in this study. We have also studied the development of this organism and its pathogenic effects have been confirmed by experimental inoculation. The alterations in the blood of the host were observed and we noted that the nucleus of the red blood cells is severely disturbed during the development of the infection. The experimental inoculation (in Leptodactylus and Bufo) have demonstred specific infectivety which is generaly hard, finishing with the death of the host. The taxonomic aspects related to this genus are discussed and the authors agree to the point of view of Mackerras 1961, and Marquardt 1967, about the identity of Pirhemocyton and Toddia. We need more research to stablish the viral nature of this organism.