Toxoplasmosis is considered to be a fatal parasitic disease in New World primates. The objective of this report was to describe, through a retrospective study, the toxoplasmosis cases in New World primates. From 1999 to 2009 eighty-six anatomopathological exams was performed in primates and toxoplasmosis was the most common disease (7/86). One case occurred in Black-Tufted-Marmoset (Callithrix penicillata) and six in Brown-Howler monkeys (Alouatta guariba). Two monkeys were found death and five died within few days. The most common clinical signs were apathy and anorexia (5/7), abdominal distension (4/7) and fever (3/7). The main gross lesions were splenomegaly (4/7), hemorrhage in digestory system, lymph nodes and urinary bladder (4/7), reddish lungs (3/7) and hepatomegaly (2/7). Histopathological findings were necrotizing hepatitis (7/7), splenitis (3/7), myocarditis (2/7), enteritis (2/7), lymphadenitis (1/7) and sialitis (1/7), and interstitial pneumonia (4/7). In the liver, lungs, spleen, heart, lymph nodes and salivary gland there were tachyzoites of Toxoplasma gondii that also detected by immunohistochemistry against T. gondii in liver, spleen and lungs (5/7). Toxoplasmosis can cause high mortality in New World primate colonies and can be a threat to preservation of those species in captivity. Therefore, preventive measures should be taken to avoid the contamination of those animals. período de 1999-2009 foram realizados 86 exames anatomopatológicos em primatas e a toxoplasmose foi a enfermidade mais comum (7/86), relatando-se um caso em sagui-do-tufo-preto (Callithrix penicillata) e seis em bugio--ruivo (Alouatta guariba). Dois animais foram encontrados mortos e cinco morreram em poucos dias. Os sinais clínicos mais frequentes foram apatia e anorexia (5/7), distensão abdominal (4/7) e febre (3/7). Na necropsia observou--se esplenomegalia (4/7), hemorragia do trato digestório, linfonodos e bexiga (4/7), pulmões avermelhados (3/7) e hepatomegalia (2/7). No exame histopatológico evidenciou-se hepatite (7/7), esplenite (3/7), miocardite (2/7), enterite (2/7), linfadenite (1/7) e sialite (1/7) necróticas e, pneumonia intersticial (4/7). Em fígado, pulmões, baço, coração, linfonodos e glândula salivar havia taquizoítos de Toxoplasma gondii que foram também detectados pelo exame de imuno-histoquímica anti-T. gondii em fígado, baço e pul-