This study describes the sexual behaviour of the adult male and female tammar wallaby from the time a female gives birth to the end of post-partum oestrus. Eleven females were continuously observed from around the time of birth until up to 3 h after the last observed mating attempt. Males began to associate with females from around the time of birth, thus females appear to be attractive to males at, but not prior to parturition. Females subsequently allowed males to mate with them from 1.3±0.8h (mean±S.D.) post-partum, although the first ejaculation was delayed until 1.8±0.8h after birth owing to intense intermale aggression directed towards any male which attempted to mate with an oestrous female. Mating chases, in which a post-partum female was pursued by several males, were observed from 1.3±0.8h post-partum. All of this mating activity usually occurred within the first 6h after birth.