Anemia is a common problem in sick dogs, and immune-mediated hemolytic anemia (IMHA) is one of the most common causes of anemia in dogs. Since death can occur rapidly in dogs with IMHA even with appropriate treatment, it is important to differentiate IMHA from other causes of anemia in its first stages. To diagnose underlying diseases in anemic dogs and differentiate IMHA cases from others, 29 patient dogs suffering from severe anemia that had been referred to Veterinary Medical Teaching Hospital at a National University from June 2004 to April 2005 were examined. The most common cause of anemia in the patient dogs was found to be liver disease accounting for 31.0% (9/29) of all, and the second most common was IMHA with 13.7% (4/29). Four dogs confirmed as IMHA cases all reacted positive to direct anti-globulin test and showed spherocytes and polychromatic erythrocytes in the blood smear. Most of the IMHA cases (3/4) were female aged 2 to 7 years and were in a severe state of anemia with less than 20% of PCV.