To clarify clinicopathologic features of idiopathic chronic pancreatitis with lymphoplasmacytic infiltration, we carried out a study of 35 cases. There were two histologic groups, which we have designated lymphoplasmacytic sclerosing pancreatitis and idiopathic duct-centric chronic pancreatitis. Lymphoplasmacytic sclerosing pancreatitis (22 cases) was a fibrosing process with diffuse lymphoplasmacytic infiltrates involving pancreatic lobules and ducts, adipose tissue, blood vessels, and common bile duct. Obliterative phlebitis was found in every case except for one. The histologic features were similar to other idiopathic fibrosclerosing disorders, and one patient also had retroperitoneal fibrosis. Affected patients tended to be elderly men. Idiopathic duct-centric chronic pancreatitis (13 cases) was characterized by inflammatory infiltrates (including neutrophils) that were denser in the lobules than in interlobular fibrotic areas. Neutrophils were also prominent in the ducts, and destruction of the duct epithelium was commonly seen. Patient ages were more broadly distributed than in lymphoplasmacytic sclerosing pancreatitis. Two patients had inflammatory bowel disease. We conclude that idiopathic chronic pancreatitis with lymphoplasmacytic infiltration, sometimes called autoimmune pancreatitis, consists of at least two different processes. One of these, lymphoplasmacytic sclerosing pancreatitis, is a histologically unique lesion and could be a pancreatic manifestation of idiopathic fibrosclerosing disorders.