One troop of red colobus monkeys (Colobus badius tephrosceles) was observed in the Gombe National Park (Tanzania) and two other troops in the Kibale Forest Reserve (Uganda). The proportions of time spent in different activities by the animals were measured by counting, at quarter-hourly intervals, the number of animals visible which were engaged in different activities. The animals spent approximately 30 % of the daytime feeding and 60 % inactive. Males spent rather less time feeding and more time inactive than females or adolescents. Within each troop, feeding activity was closely synchronized. Peaks of feeding activity usually occurred in the first half of the morning and in the second half of the afternoon. At least one feeding bout occurred in the intervening period on most days, often during the midday period.