After a review of the experimental toxoplasmosis in non human primates we have reported our unsuccessful tentatives to provoke acute and fatal disease in 2 Macacca mulatta, an infant male and an young female, by inoculation and reinoculation of a human strain from congenital toxoplasmosis, using several routse and massive dosis and with the ministration of corticosteroids. We did not succeed in inducing fatal disease in an adult female Cebus apella by peritoneal and subcutaneous routes. However, the toxoplasmosis infection in these 3 monkeys was comproved by fever (39 to 41ºC), by the positivity of the Sabin-Feldman reaction (1:64 and 1:256) and by the isolation of the toxoplasmes from mice inoculated with material of the Cebus. On the other hand, in a Callithrix jacchus by peritoneal route, we have provoked severe and fatal disease with necrotic foci in the lever and spleen both plenty of parasites, and isolation of toxoplasmes from mice inoculated with material of this monkey. From 54 New World monkeys submeted to the dye test, with the exception of a Saimiri sciureu that reacted at 1:16 title, all of them were negative. An analysis of the problem toxoplasmosis-non human primates, based in the bibliography and in our observation (see the anterior paper too) agree with the following conclusions: a) in its natural habitat the non human primates are not exposed to Toxoplasma infection. This fact must be related to its arboreal habits and vegetarian and insectivorous feeding; b) the described cases of spontaneous toxoplasmosis in monkeys are related to animals in cages; and at this very condition the natural infection of the catharrhinus monkeys presented a great resistence to the experimental toxoplasmosis and these resistence is not due to circulating antibodies. These resistence seems to be not broken by the ministration of corticosteroids. However these resistence is broken sometimes by massive dosis of parasites and generally in the young animals; d) these resistence is smaller in the platyrrhinus monkeys and it seems to be absent in the inferior platyrrhinus and in the Prosimii.