Ovulation rates were determined in 41 Yorkshire, 46 Lacombe and 26 Lacombe × Yorkshire gilts, and in 37 Yorkshire and 32 Lacombe primiparous sows. Ovulation rates in gilts remained constant from puberty to the fifth estrus. For Yorkshire, Lacombe and crossbred gilts the ovulation rates were 12.2, 14.4 and 14.0, respectively. The ovulation rates in Yorkshire and Lacombe sows were the same (17.0). In sows, ovulation rate increased significantly from the first to second post-weaning estrus (15.4 vs. 17.5). In Yorkshire gilts, ovarian and uterine weights were significantly less than in Lacombe gilts. Within breeds, ovarian weight remained similar while uterine weight increased (P < 0.05) from the first to second estrus. In sows, ovarian weight, which was similar for both breeds, increased significantly from the first to second post-weaning estrus. Uterine weight in Lacombe sows was significantly greater than in Yorkshire sows, and increased (P < 0.05) from the first to third post-weaning estrus. In Yorkshire sows uterine weight remained constant over the first three estrous periods after weaning.