The goal of the study was morphohistological changes in the peritoneum on the background of treatment of peritonitis with use of stage ablation of abdominal cavity. Materials and methods. The material has been made with peritoneal biopsy from 39 patients with peritonitis, 15 of which — with a single operation, and 24 — with multiple abdominal sanitization. The last one shave been divided into several groups, depending on the number of sanations and outcomes. For histological examination, pieces of peritoneum were fixed in a 10% solution of neutral formalin. After the appropriate wiring, the paraffin sections were stained with hematoxylin-eosin, Van Gieson at the connective tissue, in Mallory’s fibrin, and with Schiff’s glycogen reagent (controlled for amylase). Results of the conducted studies indicate: severe violations of vascular hemostasis with dystrophic changes, sloughing, focal absence of endotheliocytes, which is accompanied by sludge and perdiapedesis hemorrhages. The increase in the severity of these changes corresponds to the severity of peritoneal injury and is parallel to the growth of peritoneum permeation by microorganisms, the toxins of which cause damage to endotheliocytes; the existing mismatch of the coagulation-fibrinolytic system in the form of local intravascular coagulation; frequency and severity of fibrinoid necrosis of the vascular wall increases along with the severity of peritonitis and an increase in the number of sanations and is associated with microbial infections and the development of the allergic component of inflammation. Conclusion. The indicator of unfavorable course of peritonitis is, according to our data, the formation of local urinary incidence coagulation associated with microflora and microcirculation disorders (thromboses, hemorrhages, necrosis).According to histological studies, indications for the terminal ablation of the abdominal cavity, revision of the abdominal cavity are: 1) a purulent component of inflammation; 2) the growth of colonies of microorganisms in the peritoneum, abdominal cavity, lumen of blood vessels, liver; 3) pronounced necrotizing component; 4) an abundance of fibrinous overlays. Histological indication of laparostoma closure is a decrease in the expression of the above signs, improvement of microcirculation, active proliferation of endotheliocytes and granulation tissue.