After review of hospital records and jejunal biopsy sections, 703 cases of celiac disease, including 74 cases with dermatitis herpetiformis, were identified in Edinburgh and the Lothian region up to December 31, 1979. Of these, 469 were resident in Lothian, resulting in an overall prevalence of 50/100,000 in men and 74/100,000 in women. The prevalence in men showed no significant variation with age, whereas in women age-specific prevalence varied markedly, with a peak of 126/100,000 at ages 35-44 yr and a low of 28/100,000 at ages 45-54 yr. This variation could not readily be explained, although reduced case ascertainment among women born between 1925 and 1934 could be the basis of a modest cohort effect. There was no evidence that migration or increased mortality at particular ages might be alternative explanations. In children the incidence of celiac disease, as measured by cumulative prevalence with age, increased more than twofold between 1960 and 1975, but since 1976 it has fallen sharply. The fall in incidence in children and the unexplained variations in prevalence in women provide epidemiologic evidence for the role of environmental factors other than gluten ingestion in the etiology of celiac disease.