Abstract: A retrospective study was conducted to determine the causes of bacterial diarrhea in horses Minnesota. The database of Veterinary Diagnostic Laboratory, University of Minnesota was searched over a 10 year period (2001-2010). A total of 1,260 fecal samples from diarrheic horses were received and tested. The most common pathogens found were E. coli (46%), Salmonella (27%), Clostridium perferings (19%) and Lawsonia intracellularis (8%).