In solving some of the breeding problems and treating diseases of the reproductive system, the question of diagnosis of pregnancy has occupied a prominent position in the minds of many veterinarians. The value of an accurate diagnosis of pregnancy can not be overestimated. Although biochemical tests for pregnancy are available, they are less efficient than the clinical methods now available to the veterinarian in most instances. Clinical diagnosis of pregnancy is most important in the mare and cow and is most readily made in these animals because of the availability of their internal genitalia to rectal palpation. The failure to identify an existing pregnancy may result in abortion, should the corpus luteum be expressed or the uterus douched. On the other hand, failure to identify a sterile animal will result in delay and financial loss.