Systemic lupus erythematosus in a dog, suspected systemic lupus erythematosus in a dog, and autoimmune thrombocytopenic purpura hemmorrhagica in a dog are reported. A fice-year old, female Chihuahua (Case 1) showed initially hemorrhagic diathesis and purpura hemorrhagica. Afterward, it showed polymyositis and polyarthritis. LE-cell was demonstrated on LE-cell preparation trom blood. Systemic lupus erythematosus was diagnosed. This reponded well to the immunosuppressants, but developed iatrogenic Cushing syndrome and steroid hepatopathy. A two-and-half-year old, male toy poodle (Case 2) had chief complaint of red urine. Occult blood test for the urine sediment. This did not respond at all to antibiotics and carbazochrome, which is one of systemic coagulants. LE-cell was demonstrated on LE-cell preparation from blood. This responded relatively well to immunosupressants such as prenisolone, azathioprine and cyclophosphamide. systemic lupus erythematosus is suspected. A nine-year-and-three-month old, female Maltese (Case 3), which had history of congestive heart failure and ovariohysterectomy showed purpura hemorrhagica in the skin of chest. This had severe thrombocytopenia and leukocytosis. As prednisolone was administered before immunological examination or demonstration of LE-cell, it was impossible to diagnose whether purpura hemorrhagica developed as a member of systemic lupus erythematosus or independent of systemic lupus erythematosus. This responded well to prednisolone, and so autoimmune thrombocytopenic purpura hemorrhagica was diagnosed.