A 52-year-old male developed cutaneous necrotizing vasculitis, renal failure, massive proteinuria, and elevated serum IgE levels following oral naproxen therapy. Renal biopsy specimen revealed cellular crescents in more than 40% of the glomeruli and a rare arteriole displayed thickening and eosinophilia of intima. Electron microscopic examination showed fusion of epithelial foot processes. Discontinuation of naproxen therapy was associated with disappearance of cutaneous lesions and improvement of renal function.