Eighty-one patients with dermatitis herpetiformis were treated with a gluten-free diet (GFD) for periods varying from 6 to 36 months. At the end of the treatment the daily requirement of dapsone was significantly lower in patients treated with a GFD than in 49 patients on a normal diet. 93% of the patients on a GFD were able to reduce the dose of dapsone whereas only 16% of the patients on a normal diet were able to do this. Complete remissions occurred only in patients on a GFD. 28% of the patients on a GFD were able to stop dapsone completely and were continuously asymptomatic when they observed a strict diet. A response to a GFD was noted on the mean daily requirement of dapsone as soon as the treatment was initiated although the length of time for an individual response varied. After one year on a GFD the patients needed on average about 40% and after 3 years about 20% of the dose required to control skin symptoms at the beginning of the diet. The patients responded to a GFD irrespective of changes found in the jejunal mucosa and irrespective of the presence of absence of HLA-B8.