ANNOTATION: The study was carried out on 16 30-day-old white random bred rats. Animals were withdrawn from the experiment at 30 days of age by instant decapitation of animals under ether anesthesia. After opening the abdominal cavity, the microscopic changes in the stomach were examined. Using a caliper, the anatomical parameters of the extracted stomach were measured. The stomach was fixed in 10% formalin solution and embedded in paraffin according to generally accepted rules. Then, histological sections with a thickness of 6-7 μm were prepared, which were stained with hematoxylin and eosin. Morphometric studies of the stomach tissue were carried out under a Leyka microscope. In 1-month-old rats, the total thickness of the stomach wall in its cardial part and in the place of transition to the duodenum remained unchanged, but a well-developed mucous and submucosa of the wall was revealed.