Since dwarf mongooses in captivity show an extremely stable familiar structure with no evidence of group break-up, the study was designed to place the animals under crowding stress to determine whether such tendencies would be manifested and whether compensatory mechanisms to maintain group cohesion are present. A stable family group of 12 animals was investigated and observations over 150 h under control and 120 h under crowded conditions made. The results show that social pressure is mainly exerted on subordinate adult ♂♂ and ♀♀, sometimes resulting in their death by stress-induced uraemia, through increased aggression by the a pair. The social system stabilises after 16 days but high intra-group aggression/submission remains. Synchronisation of oestrus cycles in nubile ♀♀ resulted in simultaneous littering with loss of all young. The significance of these findings for population regulation is discussed.