Among 771 children (381 Swedish and 390 Danish) investigated between 1972 and 1989 because of suspected celiac disease (CD), 179 proved to have the disease. Surprisingly only 24 CD patients were found among the Danish children, compared with 155 in the Swedish group, despite the close ethnic, geographical, and cultural background of the two populations. The Swedish CD children were diagnosed at an earlier age than the Danish children (mean, 1.5 vs. 5.5 years). The symptoms of the Swedish patients were dominated by failure to thrive (93 vs. 71%), whereas a higher proportion of the Danish CD patients suffered from stomach pain (21 vs. 5%). Breast-feeding habits were comparable. The estimated content of gliadin in the officially recommended diets of the two countries in 1987 differed substantially, the Swedish diet containing more than 40 times more gliadin than the Danish (4,400 vs. 100 mg) at the age of 8 months, and 4 times more (3,600 vs. 900 mg) at the age of 12 months. The Danish infant diet differed significantly from the Swedish in containing a larger amount of the lower gluten-containing rye flour. The earlier introduction of food items with a high gluten content in the Swedish compared with the Danish diet seems to be an obvious explanation for the great difference in incidence and symptomatology of CD between the two populations.