Based on the analysis of 235 patients with chemical burns of the esophagus and stomach and their sequelae, as well as the data of 111 pathoanatomical and medicolegal autopsies in persons, died in different periods after poisoning with corrosive substances, a burn of the duodenum and small intestine was observed in 71 cases. It was found that such factors as an intake of large doses of caustic liquors, poisoning in full stomach, especially in a state of alcohol intoxication, largely contribute to retropyloric penetration of a corrosive substance. A burn of the duodenum and small intestine would considerably aggravate the life prognosis during the first days of poisoning, and the former was observed in every second patient who died. In later period insignificant lesions disappeared completely, while at the site of deep burns an isolated or associated narrowing of the duodenum and small intestine developed. Surgical interventions were performed mainly in later periods in the presence of scarring contractions of the duodenum and small intestine, that impede an intestinal passage, and were aimed at its restoration. In the early period operations were performed only in life risk complications (intestinal hemorrhages, peritonitis), and these were of a palliative character.