The red deer (Cervus elaphus) is a seasonal breeder, mating mainly in October and calving in June. This timing is advantageous to wild deer on the hill in that the relatively high nutritional demands of lactation may be met from the abundance of summer vegetation. On low-ground pastures, however, there is an earlier start to the grazing season and the deer farmer may benefit from being able to advance calving dates. Recent research work has shown that exogenous hormone therapy can advance the breeding season in female red deer (Adam and Atkinson, 1984; Adam, Moir and Atkinson, 1985; Nowak, Elmhirst Webster and Barrell, conception and hence and Rodway, 1985; Webster; and Barrell, 1985) and that conception and hence calving dates can indeed also be advanced (Adam, 1985; Adam, Moir and Atkinson, 1986). This paper reports the effects of birth date on the performance of suckled calves and their dams under farm conditions.