Patients with dermatitis herpetiformis have been studied prospectively for 2 years to assess the effect of a gluten-free diet (GFD) on control of the skin lesions. Daily requirements for oral medication with sulphapyridine or dapsone were reduced by GFD treatment and if complete clinical remission of the skin disease occurred, it was maintained while the diet was strictly observed. However, complete remission did not occur significantly more often in GFD-treated patients than in patients taking a normal diet. Many of the latter group exhibited variation in their drug dose requirements during the period of study. GFD treatment seems desirable for the majority of patients with dermatitis herpetiformis, not only to correct the intestinal abnormality but also to minimize the dose of drugs necessary to control the skin lesions.