Abortion, according to S.J. Roberts, DVM, MS, is the expulsion of a living fetus before it reaches a viable age, or more commonly the expulsion of a dead fetus of a recognizable size at any stage of gestation. This unproductive termination of pregnancy is costly to the cattle producer and presents an enormous diagnostic task for the veterinarian in each field. A complete understanding of each cause of abortion and assistance from a diagnostic laboratory will enhance the efforts of the diagnostician in the field.