Studies were carried out to investigate the age at first calving, calving interval and birth weight of imported Aberdeen Angus, Charolais, Brahman, Hereford and their crossbreds in Cheju. The data were analyzed using the least square method. 1. Aberdeen Angus and Brahman were 0.1 and 3.1 months later at first calving than the overall mean (44.7 months) but Hereford and Charolais were 3.2 and 0.4 months earlier than the other breeds (P $lt;0.01). 2. Brahman was at the calving interval of 469.8 days; Charolais, 386.4 days; Aberdeen Angus, 390 days and Hereford, 391.8 days respectively. The age of dam has an effect on the calving interval and the shortest calving interval was observed in cows at 5-10 years of age. 3. The birth weight of Chatolais was the heaviest as 31.6㎏ and the birth weight of Aberdeen Angus was the lightest as 25.4㎏ among the purebreeds. The birth weight of Ft calves from Brahman×Hereford heavier than those of Ft calves from Charolais×Hereford and Angus×Hereford (P $lt;0.01). 4. Male calves were on average, 2.1㎏ heavier than female calves at birth weight (P $lt;0.01). There was, however, no significant difference due to season and calving order.