The length of estrus, length of the estrous cycle, dates of breeding and calving, and length of gestation were investigated for Newfoundland caribou (Rangifer tarandus). The length of heat was about 48 h and the length of the estrous cycle was thought to be 10–12 days. Breeding observed during 5 years occurred between October 9 and October 19. In 6 years of observations, 90% of the calves were born in about a 12-day period, usually between May 24 and June 5. Information is provided on the weight of calves at birth. The gestation for four wild females with adequate winter diet was 229 days.