Background: We studied changes in the stomachs of adult rats under long-term gravitational overload and under protection from it. Material and methods: The research was performed on 24 adult Wistar rats. The first group was the control one. The second one was exposed to gravitational overloads. The third group consisted of the animals under physical protection. The fourth group included animals which were under combined protection. Organometric and morphometric analysis included research of main structural units of stomach. Results: The second group had swollen loops of intestine. Serosa was dim. Vessels were dilated. Surface epithelium desquamated focally. The thickness of the gastric mucosa increased. The depth of the gastric pits was lesser. Chief cells were increased in their number. Many parietal cells were deformed, had vacuolated cytoplasm and hyperchromatic nuclei. Their number was at the reference value. The number of endocrine cells decreased. The third group had evenly inflated loops of intestine. Serosa was shiny. Mesenteric vessels somewhat expanded. The depth of the gastric pits was lesser. Chief cells had different shapes, seals and basophilic cytoplasm. The number of main and endocrine cells increased. All cells’ parameters decreased. Thus studied stomach’s parameters in fourth group changed a little and slightly. In this follow-up of the structure of stomach’s fundic glands have been saved. The number of сhief cells increased. The number of parietal cells changed insignificantly. Conclusions: Long-term gravitational overloads cause considerable changes in the macroscopic picture, and organo-cytometric parameters in stomach of adult rats. The usage of the methods of protection negates the macro- and microscopic structural changes of the stomach caused by gravitational overloads. Changes in the studied parameters were less pronounced in case of the combined method.