Antechinomys laniger is polyoestrous, and animals from Sandringham Station in south-western Queensland are in breeding condition from midwinter to midsummer. Laboratory observations suggest that photoperiod may be the proximate factor controlling the timing of the breeding season. Females enter oestrus up to six times during the season, and as the season progresses the length of the oestrous cycle decreases. The estimated length of gestation is 12 days or less. Females may rear up to six young. The young are weaned when about 3 months old and become sexually mature at 11.5 months. Both males and females are potentially capable of breeding in more than one season. Higher than average rainfall may have led to a decline in the numbers of A. laniger on Sandringham Station.