SummaryRanging patterns, feeding activity, and time budgets of a group of gray‐cheeked mangabeys in the Kibale Forest, western Uganda, were studied in May‐June 1971 and from March 1972 to April 1973. Locations and activities of individuals in a fifteen‐member group of this arboreal primate were systematically recorded at half‐hourly intervals during continuous following of the group. Phenological data were concurrently collected for eleven species of intensively used trees. Mangabeys are primarily frugivores, although leaves and flowers of some species are eaten and substantial time was devoted to insect foraging.Although a typical twice‐yearly alternation of wet and dry periods exists in this forest, strongly seasonal trends are the exception in the following aspects of mangabey behaviour: (1) extent and location of areas used, (2) distance moved daily, (3) percentage of time spent feeding or moving, (4) percentage of time spent feeding on different food types. An explanation may be provided by the phenological data, which indicate that many species of tree used by mangabeys fruit either asynchronously and nonseasonally or synchronously but at very long and possibly irregular intervals. Thus mangabeys are faced with foods which fluctuate widely in availability, particularly within a small area, but which are not seasonal in their flu