On small and intermediate farms, cows inseminated in the winter or spring had more AI per conception than those inseminated during the summer or autumn (P < 0.05), but no seasonal difference was found on large farms. A difference in the number of AI per conception between herd size groups was found only during the winter and spring (P < 0.05). Cows on small farms had more AI per conception than those on large farms only at parities 5 to 7 (P < 0.05). In cows first served at 95 days or more after calving, there was no difference in the number of AI per conception between herd size groups.