In a subset of patients attending liver units, a chronic increase in serum transaminases may remain of undetermined cause despite thorough investigations. On the other hand, elevated levels of serum transaminases have been reported in about 40% of adult celiac patients. To evaluate the prevalence of subclinical celiac disease in patients with chronic unexplained hypertransaminasemia in comparison with that in the general population (0.5%), 140 consecutive patients with chronic increases of serum transaminases levels of unknown cause were tested for antigliadin and antiendomysium IgA antibodies. All patients with positive antibody tests were offered upper gastrointestinal endoscopy with distal duodenal biopsy. Thirteen patients (9.3%, 95% confidence interval 5. 0-15.4) had positive antigliadin and antiendomysium antibodies. The prevalence of antibodies was 17% in women and 5.4% in men (8/47 vs. 5/93 respectively; relative risk 3.2, 95% confidence interval 1.1-9. 1). Distal duodenal biopsy performed in all but one of the patients showed mild villous atrophy with increased intraepithelial lymphocytes in three cases, subtotal villous atrophy in six, and total villous atrophy in three. The prevalence of celiac disease in the patient group was significantly higher than that in the general population (P <.001) with a relative risk of 18.6 (95% confidence interval 11.1-31.2). On the basis of the present findings, screening for celiac disease is an important tool in the initial diagnostic work-up of patients with chronic unexplained hypertransaminasemia.