This study investigated the risk factors for diabetes mellitus in dogs reviewing medical records of 1019 dogs with diabetes mellitus (DM) from university veterinary hospitals (VMDP) and 449 dogs from a private veterinary hospital (AMC) as well as control cases. Risk was higher for entire and neutered females compared to entire males, especially at older ages. Poodles showed a significant excess risk, and German Shepherds, Cocker Spaniels, Collies and Boxers had a significant lower risk.