Abstract: The disastrous effect of replanting Eucalyptus trees in place of natural forest in South India for short term economic benefits is rapidly causing the deterioration of the fauna indigenous to South India (Daniel & Kannan 1967). The Nilgiri langur, Presbytis johni, is one such endangered species. This monkey is endemic to the evergreen shola areas in the Nilgiri mountains. This papers offers data on food habitats and some range of three troops of langurs that wear studied at Periyar sanctuary in Kerala from March to May 13,1968, for about 270 contact hours.the period of study just prior to the rainy season, was one of transition in vegetational growth, which enabled observations to be made on the changing diet of these monkeys.