Eleven diabetic patients with biopsy-proven IgA nephropathy were studied. Seven exhibited coexistence of both IgA nephropathy and diabetic glomerulosclerosis and the remaining four patients had IgA nephropathy without diabetic lesion. The clinicopathological features and follow-up of those patients with IgA nephropathy surperimposed on diabetic glomerulosclerosis were compared with a similar group of patients with diabetic glomerulosclerosis alone. Our observation suggests that the occurrence of both glomerulopathies was fortuitous with IgA nephropathy coexisting with or preceding diabetic glomerulosclerosis. There was no apparent causal relationship between the two glomerulopathies. The renal outcome is poor in both groups of patients and is possibly related to diabetic glomerulosclerosis.