Since Kahn et al. reported in 1976 insulin resistant diabetes due to anti-insulin receptor antibodies, an unusual form of diabetes mellitus (type B) has been found in many countries. We had two diabetic patients with anti-insulin receptor antibodies, associated with either acanthosis nigricans or systemic lupus erythematosus. Remission occurred 15 months after the onset of insulin resistant diabetes. One patient unfortunately died of acute pneumonia and the other has been followed up. The anti-insulin receptor antibodies were measured according to the method of Omori and Hirata by using the pellet of human placental membrane. The anti-insulin receptor antibodies in both cases diminished as remission occurred. Reverse hemolytic plaque assay (PFG) detected immunoglobulin-producing cells. In Case 2, the plaque forming cells were twenty times as many as the normal value. Immunosuppressive therapy with cyclophosphamide reduced the immunoglobulin secreting cells as remission occurred. The patients with insulin resistance (type B) should be treated with enough insulin inspite of the presence of insulin resistance. Besides, cyclophosphamide, 6-mercaptopurine and prednisolone should be used with caution. Plasma exchange is a treatment to be tried. It is important to note that spontaneous remission may occur more than half a year after the onset of insulin resistant diabetes.