Methods of light-optical microscopy, morpho- and cytometry and histochemisty were used to study the epithelial lining of herbal's small gut after 12-day flight in biosat "Foton M3". Changes in mucous coat histoarchitectonics included branching of villi and cystic lumps lined with prismatic epithelium. Shortening of the mucous membrane villi was accompanied by reduction of prismatic epithelium height, increase in the number of goblet cells and change of their dislocation, stimulation of excretion of biosynthesis products on the brush border surface pointing to impairment of the interstitial barrier function. Nothing evidenced change in mitotic index of the crypts epithelium in animals of the vivarium control, in the Kontur facility simulating the flight condition, and in the space flown herbals. There was a minor individual variability of changes in the epithelium mucous membrane due to the simulated flight factors.