In a defined area of 273 000 inhabitants in Central Sweden a total number of 125 patients with dermatitis herpetiformis (DH) were observed during the years 1974-1982. The incidence was calculated for the years 1943-1982 and was found to be 0.86-1.45 patients/100 000 inhabitants/year, which is in agreement with a report from Finland. However, the prevalence of DH in the area was 39.2 patients/100 000 inhabitants, which is much higher than previously reported. Spontaneous transient remissions of more than half a year duration were seen in 20% of the patients. At the end of the study, 16 out of 37 patients (43%) on normal diet used no dapsone because of no or minimal rash. Immunohistochemical demonstration of IgA-deposits at the dermoepidermal junction was found to be a good diagnostic criterion. Granular deposits were seen in all except one patient, also in those needing no dapsone. Five out of 6 patients with a granular-linear pattern were still alive at the end of the study, and all of them needed dapsone for control of the rash.