Celiac disease (CD) is an underdiagnosed disease occurring in different clinical forms. This study aimed to determine the prevalence of CD among blood donors from Ribeirão Preto, Brazil, and to study some demographic characteristics of celiac patients. Blood samples from 3000 blood donors were tested for the presence of tissue transglutaminase antibody and positive samples were tested for endomysial antibody. Donors positive to both tests were referred for clinical evaluation and for a jejunal biopsy. Twenty-four samples were moderately/strongly positive for transglutaminase, with 9 of them being endomysial negative and 15 positive. Of the 13 biopsies obtained from 12 females and 1 male, 1 was classified as Marsh grade IV, 4 as grade III, 2 as grade II, 4 as grade I, and 2 as grade 0. Estimated prevalence was therefore 1:273 (0.33%; 95% CI, 0.127 to 0.539). The 1:273 estimated prevalence of CD detected indicates that the disease is not rare in Brazil. The frequency was higher among females and among individuals of European descent, with a significantly higher frequency for a family history of digestive tract cancer or epilepsy.