This is a discussion of a two year study on vaccination in the prevention of bovine E. Coli Diarrhea. Investigations have demonstrated many causes of diarrhea in calves, including management and infectious agents (34, 73). The infectious agents presently recognized as the causative agents of diarrhea include many viruses such as rotavirus, IBR and BVD. In addition, bacteria including the Salmonella spp., Clostridium spp., and Escherichia coli (E. coli) have frequently been associated with calf diarrhea (84)