A 51-yr-old man, who presented with diabetes mellitus, abdominal pain, inguinal lymphadenopathy, and diffuse enlargement of the whole pancreas on ultrasonography, was at first thought to have pancreatic lymphoma. Chemotherapy including steroid was carried out successfully, although the definitive diagnosis of lymphoma was not made. However, on follow-up, we realized that both laboratory findings, such as hyperglobulinemia and autoantibody-positive results, and radiographic features in this case were very similar to those of a case of autoimmune pancreatitis recently reported by Yoshida et al. (Dig Dis Sci 1995;40:1561-8). When the disease recurred, therefore, treatment with steroid alone was performed with an excellent result. We report a case of autoimmune pancreatitis simulating primary pancreatic lymphoma.