Vegetative forms of 4 strains of Toxoplasma from peritoneal fluid of mice with 3-4 days of acute infection were orally administered to 4 groups of 6 newborn and wealing kittens respectivelly. Each group had a control kitten. All kittens were observed for eriods of 6-20 days ans never passed in their faeces oocysts attributabel to T. gondii. On the other hand, their faces after 2-4 days in potassium dichromate at 2.5% inoculated orally in mice didn't produce Toxoplasma infection in these animals; and with exception of the cats that have had spontaneous isosporosis (I. felis and/or I. rivolta) we didn´t see evolutive forms of Coccidia in the intestinal wall of the cats. In all cat groups the toxoplasmic infection was comproved by the positivity of the dye-test (1:16 to 1:1.024) and by the isolation of toxoplasms in indicator mice inoculated with material from cat´s principal organs. Several of the wealing and newborn kittens were diseased and some died of systhemic toxoplasmosis: splenitis, hepatitis, pneumonitis, miocarditis and encephalitis, with numerous parasites.