We report a patient with Churg-Strauss syndrome-associated rapidly progressive glomerulonephritis concurrent with diabetes mellitus. The patient was a 64-year-old woman who was admitted to our hospital because of a glove and stocking type hypesthesia and numbness, multiple purpurae on both legs, and renal insufficiency with hematuria and proteinuria. Renal biopsy revealed necrotizing crescentic glomerulonephritis accompanied by necrotizing arteritis, marked eosinophilic infiltration of the interstitium, and diffuse and nodular diabetic glomerulosclerosis. Cyclophosphamide and steroid therapy succeeded in improving her neurologic symptoms as well as retarding the deterioration in renal function. No clinical manifestations suggestive of a recurrence of Churg-Strauss syndrome have been observed during the one-year follow-up period.