The issues of etiotropic therapy of infectious diarrhea require a differentiated approach not only depending on the etiological factor, but also on the type of diarrhea caused by the location of the pathological process. Infectious diarrhea occur in the form of three main types: secretory, osmotic, inflammatory (invasive). Secretory and osmotic type of diarrhea are found in infectious gastroenteritis. In the mechanisms of elimination of infectious gastroenteritis pathogens, the following factors play a leading role: the destructive effect on pathogens in the lumen of the small intestine of trypsin, chemotrypsin and acid duodenal content entering the small intestine; the «killer» action of interepithelial large granular lymphocytes (M-cells) on pathogens; the increase in resistance of the small intestine epithelium under the influence of M-cell cytokines; the difficulty of intercellular distribution of pathogens due to faster than in the gut, small intestine epithelial cell renewal; microbial antagonism of representatives of normal intestinal microflora. The appointment of etiotropic agents in cases of infectious gastroenteritis, at least, suppresses the manifestations of microbial antagonism on the part of representatives of the normal intestinal microflora, creating prerequisites for the delay of the pathogen in the body. The inflammatory type of diarrhoea occurs when invasion of pathogens to the mucosal lining of the colon, with subsequent development of the destructive changes and the possibility of further translocation. Obstacles to adhesion, penetration and intercellular spread of invasive pathogens in the colon mucosa is much less than in the small intestine. Pathogens of the same genera, species and serological variants (e.g. Salmonella, Campylobacter) can cause both secretory and invasive types of diarrhea. However, the appointment of antibacterial therapy will depend on the location of the pathological process. When gastroenteritis etiotropic therapy in most cases is impractical. In the presence of clinical manifestations of colitis, involving the implementation of invasive properties of the causative agent, the appointment of etiotropic treatment is justified.