A fine-needle kidney biopsy was performed on eleven patients with dermatitis herpetiformis (DH) who had no previous signs or symptoms of renal disease. Of the eight patients whose biopsy specimens were representative, electron microscopic examination showed mesangial deposits in five. A subsequent conventional renal biopsy was obtained from one of these five, and immunofluorescence microscopy revealed IgA and complement deposits in the glomeruli. Renal involvement was not related either to the degree of jejunal villous atrophy or to the deposition of IgA and complement in the skin. Glomerular deposits, however, were associated with a high frequency of circulating IgA and IgG class immune complexes and IgA class antigliadin and antireticulin antibodies. These results suggest that, in DH, immune complexes or antibodies derived from the gut can be deposited in the kidney.