Information on intestinal microecological disturbances (dysbacteriosis) and the preparations of probiotics, prebiotics and synbiotics used for the correction of resident normal colon microflora is presented. Probiotics are preparations containing live microbes or substances of microbial origin that, when introduced by natural methods are expected to confer beneficial physiologic, biochemical and immune effects to the host through the stabilization and the optimization of functions of normal microflora. Prebiotics are preparations containing a non-digestible food ingredient that beneficially affect the host by selectively stimulating the growth and the activity of a limited number of resident bacteria of normal microflora in the colon. Synbiotics are preparations obtained as the result of the rational combination of probiotics and prebiotics.