Forms of aggression, their situational motivations and frequencies in Thomson's gazelle were investigated to elucidate the multiple functions of aggressive behavior as well as quantitative differences in encounters with opponents of different sex, age, and social classes. The study was conducted in the Serengeti National Park (Tanzania) where the gazelle population is estimated to total 600 000. Within three years, 4016 agonistic encounters were recorded and analyzed. Besides the confirmation of its conventionally recognized functions in territoriality, etc., the great role of intraspecific aggression in the coordination of group activities appears to be of special importance.