We reviewed 18 patients with a clinical diagnosis of dermatitis herpetiformis who were being treated with dapsone and were on an unrestricted diet. Diagnosis was confirmed by finding IgA deposits in the dermal papillae of unaffected skin. Dapsone was discontinued and biopsy of affected skin was carried out when the typical rash reappeared. The biopsy findings were graded according to the severity of the histological changes. Small bowel tissue from each patient was examined and graded by stereo- and routine microscopy. Thirteen specimens (72%) were stereomicroscopically abnormal; all 18 showed villous atrophy, either partial or subtotal; and in 13 (72%) the interepithelial lymphocyte count was increased. No correlation was found between the histological severity of the skin and the small bowel lesions. Seemingly the severity of the skin rash in dermatitis herpetiformis is no guide to the degree of small bowel abnormality.