The prevalence of celiac disease (CD) was determined in healthy blood donors and in high-risk groups of adults (a total of 1835 adults--randomly selected 1312 healthy blood donors, 102 patients with primary osteoporosis, 58 patients with autoimmune diseases and 365 infertile women). It was calculated on the basis of a two-step serologic screening method--in the first step IgA and IgG antigliadin antibodies (AGA) and IgA anti-gamma-glutamyltransferase ('transglutaminase') antibodies (ATG) were estimated, in the second step sera positive for IgA AGA and/or IgA ATG were examined for antiendomysial IgA (AEA) antibodies. Immunoenzymic assay (ELISA) was used for determining of AGA and ATG antibodies; immunofluorescence method, performed on human umbilical cord tissue, was used for assaying of AEA antibodies. Total serum IgA level in only IgG AGA positive subjects was measured by routine turbidimetric method. 0.45% of healthy blood donors, 0.98% of osteoporotic patients, 2.7% of patients suffering from autoimmune disease and 1.13% of women with infertility considered as immunologically mediated were found to be positive in both steps of serologic screening (AGA and/or ATG and antiendomysium positive). The presumed high prevalence of seropositivity for CD in apparently healthy Czech adult population was confirmed. In the high-risk groups, the prevalence of seropositivity for CD was approximately 2-4 times higher than in healthy blood donors. The real prevalence of CD in the tested groups, however, can be estimated after performing small intestinal biopsy in the seropositive patients.