Aim. To perform a comprehensive study of intestinal digestion, absorption, and microbiocenosis in various stages of cholelithiasis (CL). Subjects and methods. A total of 76 patients with of CL, including 44 patients with its Stage I and 32 patients with Stage II, were examined. Mono-, di - and polysaccharide load tests and a scatological study were performed to evaluate the processes of digestion and absorption in the intestine. The hydrogen breath test using lactulose was carried out to study small intestinal bacterial overgrowth (SIBO). The state of colon microbiocenosis was determined by plating feces onto various selective nutrient media. Results. All digestive process stages in the small intestine were noted to be impaired in CL. In Stage I CL, cavitary digestion was mainly impaired; in Stage II, all digestive and absorptive processes were abnormal. Scatological examination in patients with Stage I CL revealed steatorrhea in 79.5%, creatorrhea in 75%, and amylorrhea in 36.4%. In Stage II CL, digestive and absorptive disorders progressed. SIBO was detected in 68.5% whereas in 70% of cases, it was located in the distal small intestine in the presence of insufficiency of the ileocecal sphincter apparatus. A regularity was found between the severity of SIBO and impaired small intestinal cavitary digestion. SIBO was more common in the pre-gallstone stage of CL than in its gallstone stage. Dysbiosis of the colon was detected in 100% of the examined patients with CL; moreover, as the latter progressed, dysbiosis worsened. Conclusion. There is new information about impaired intestinal digestion and microbiocenosis in patients with CL.