Although this is based on only ones years’ results, it indicates that the breeding potential of yearling bulls can be determined before they are run with a cow herd. In this test one bull sired the majority of the calves and generally was the bull predetermined to be the active breeder. Results of the test suggest that a good, active, breeding yearling bull is capable of breeding more than 12 to 15 cows as is normally recommended. In our studies, one yearling bull sired up to 36 calves in a 45-day breeding season. Possible adverse effects of using a yearling bull that much are being evaluated.