Frequencies of stereotyped lek displays of male Drosophila grimshawi were measured in groups of different sizes (2, 4, 8, or 16 ♂♂ per container). In one experiment ♀♀ were absent, and in a second experiment two ♀♀ were present in each male group. In both experiments the frequency of courtship displays was linearly dependent upon density. Two agonistic displays and a communal display were density-dependent only when ♀♀ were present. The strategy ♂♂ adopted only in the presence of ♀♀ was: (1) to balance the relative frequencies of communal and aggressive behavior, and (2) to increase the ratio of contact to noncontact aggression with increasing density.