Summary 1. Purebred dairy bulls vary greatly in their ability to transmit producing capacity to their offspring. 2. This is not a breed characteristic. 3. In determining the value of a bull the difficulties he has to overcome must be taken into consideration. When a bull is mated to high producing cows it is not always easy to have the next generation producing much better than their dams. 4. Animals of the same or similar breeding may vary greatly in producing ability due to individual characteristics. 5. Difficulty will sometimes be found in getting a bull that will “nick” properly with all the cows in a herd. 6. If the production of a herd is to be increased rigid selection on the basis of production must accompany intelligent breeding.