The occurrence of immunoglobulin A nephropathy (IgAN) in patients with noninsulin dependent diabetes mellitus (NIDDM) is a rare event and of pathogenetic interest. It is not clear whether this is merely coincidence. We report here five patients with IgAN in NIDDM associated with or without diabetic glomerulosclerosis. All of the patients were Korean males. In three patients, diabetes mellitus was diagnosed at the same time with diagnosis of IgAN, and the known duration of the diabetes in the other two patients were three and seven years, respectively. There was no evidence of diabetic retinopathy in four patients, but it was found in one patient. In all cases, the diagnosis of IgAN was made by immunohistology.