Non human primates form an integral part of biodiversity and a cognizable link between human and nature. Many of the non human primates species are using as laboratory animals for medical research due to their similarities with human. Northeast India is rich for primate diversity having as many as 11 species of non human primates. Deforestation has disturbed the population dynamics posing a major threat for the survival of this species. Habitat destruction, encroachment and huntings are the major threats for these valuable animals in this region. The conservation of these wild animals is necessary as they maintain the ecological balance. For preservation and conservation of these animals, the study of their pathological condition is of utmost important. Keeping the above facts in view, the present study is undertaken to know the causes of death of non human primates along with the study of their atherosclerotic lesions, parasitic infections and sero-prevalence of hepatitis A virus infection. The study recorded 12 different causes of death, 2 atherosclerotic lesions, 2 different parasitic infestations and 10 positive blood samples for hepatitis A virus infection.