A 16-month study of foraging and ranging among gray langurs (Presbytis entellus) in the Nepal Himalaya revealed that these animals range over larger areas than other gray langurs so far studied and that they show great seasonal differences in foraging and ranging. A summer monsoon and winter dry season characterize the Himalayan climate. During summer, broadleaf forest provides the basic foraging substrate for the langurs, and when its resources fail during the winter dry season, they radically shift their diet and feed largely in meadow, range over wider areas, use their range more evenly and make longer day journeys. It is hypothesized that the ability of the langurs to make these changes in response to the dry season is vital to their survival at the study site.