Aim. To clinically evaluate the activity of glucoamylase, maltase, saccharase, and lactase in the small intestinal mucosa (SIM) of patients with celiac disease. Subjects and methods. Twenty-nine patents with celiac disease were examined. The disease was first detected in 8 patients; in the remaining patients, it had been diagnosed 6 months to 35 years before. The diagnosis was verified by histological examinations of duodenal biopsy specimens and by determination of immunoglobulin (Ig) A and G antibodies to tissue transglutaminase (atTG) and gliadin (AGA) by an enzyme-linked immunosorbent assay (ELISA). Carbohydrase activities were estimated in the duodenal biopsy specimens, by applying the method of A. Dahlquist. Results. In the control group, the activities of glucoamylase, maltase, saccharase, and lactase averaged 598.8±184.2, 825.3±239.3, 180.2±68.1, and 53.4±16.3 ng/glucose/mg tissue min, respectively. In the patients with celiac disease, the average activities of all the examined enteric enzymes were significantly below the normal value even they had been on a gluten-free diet (GFD) for 10 years or longer. Complete SIM structural recovery (Marsh stage 0) occurred in only 7 of 18 patients who had been on a strictly GFD. Serological (atTG and AGA) tests got also negative in all the 7 patients with completely recovered SIM.  Six of the latter patients continued to have abdominal bloating and borborygmus, unstable stool with a propensity for diarrhea and weakness. Each was detected to have a lower activity of one or a few enzymes. The activity of all the carbohydrases reached its normal value in only 1 patient and she felt healthy, without perceiving any food intolerance. Conclusion. The activity of membrane enzymes may serve as a marker for the degree of SIM recovery in patients with celiac disease.