Aim of investigation: to assess the effectiveness and tolerance of dietary supplements (BAA) STIM and STIM LaxMaterials and methods: The analysis of the treatment of 73 patients who were divided into 2 groups. Group 1-32 patients with functional constipation (8 men and 24 women; mean age — 45.7 ± 12.4 years), Group 2-41 patients with functional diarrhea (19 men and 22 women; mean age — 41.0 ± 15,8 years). The study of clinical symptoms was carried out according to the data of an individual diary, using specialized questionnaires with a scoring of symptoms before and after the course of treatment, before and after treatment, the result of the carbolene test, the content of short-chain fatty acids in the feces was assessed. Tolerability was assessed by recording side effects and adverse events.Monotherapy was carried out with STIM LAX for patients with functional constipation at a dose of 1 tablet 3 times a day for 30 days. STIM for patients with functional diarrhea was prescribed in a dose of 2 tablets 3 times a day for 30 days.Results of the study: The results of the study showed that FC therapy with StimLax effectively reduces the frequency and intensity of symptoms such as difficulty / pain, discomfort during defecation, feeling of incomplete emptying, abdominal pain, time spent in the toilet and the number of failed bowel movements. We observed the normalization of transit time according to the carbolene test and an increase in stool frequency up to 5 times a week.Treatment of patients with FD with Stim led to a significant decrease in the intensity of abdominal pain, rumbling, flatulence, stool frequency, an increase in the time of the carbolene test and the normalization of its consistency.Adverse events were observed in 8 (10.9%) patients (4 patients with FD and 4 patients with FD). On the 3-5th day of treatment, there was an increase in flatulence, rumbling in the abdomen. A temporary decrease in the dose of the drug to 1-2 tablets per day removed these phenomena and the symptoms that appeared were resolved within 1-3 days. After that, the dose of the drug was gradually increased to the initial (effective), which the patients tolerated normally.Conclusions: The results of this study indicate high clinical efficacy and good tolerability of treatment with drugs StimLax and Stim in patients with FC and FD. In some cases, it is necessary to titrate the dose of the drug (downward), but this is not accompanied by a decrease in the effectiveness of therapy. The use of these drugs with metaprebiotic properties helps to modify the microbiota of patients with functional bowel diseases. With constipation, the number and activity of both lactic acid flora and microorganisms that produce butyric acid are stimulated; in addition, calcium lactate is an additional source of butyric acid due to metabolism. With diarrhea, along with the stimulation of the number and activity of the lactic acid flora, there is an improvement in the utilization of butyrate by intestinal cells.