Mast cells (MC) produce, store and release many biologically active substances, especially inflammatory factors, chemotactic substances for neutrophiles, cytokines and prostaglandins. They play very important role in fibrinosis and they are an important factor in peritoneal adhesions formation and lysis. In this study we tried to evaluate role of mast cells in peritoneal adhesions formation. We estimated number of mast cells in peritoneal fluid in rats with experimentally developed peritoneal adhesions. The number of mast cells per ml was counted in flow cytometry in specimens of peritoneal fluid taken from operated rats. The fluid was taken in standardized conditions the same for each group at the first operation and during reoperation. Peritoneal cavity was washed with 0.9% Saline solution. MC were visualized using indirect immunohistochemical method LSAB with mouse antibody. The animals were divided into 4 groups. 1 st group was control group (n=20) on which the abdomen was opened and closed without any manipulations, and the reoperation was done after 72 hours. The other groups (2, 3, 4; n=20 for each group) were operated and scarification of the partial peritoneum and serosa was performed. The rats were brought back to conscious and then were reoperated respectively after 24, 72 and 168 hours after first surgery. After the laparotomy and damage of the peritoneum we observed formation of the peritoneal adhesions between intestine loops and between intestines and damaged parietal peritoneum. Also the higher number of mast cells was observed in the groups of animals with damaged peritoneum. The highest number of peritoneal adhesions was observed in the group of animals reoperated after 72 hours. After 72 and 168 hours the higher number of MC and neutrophils was observed. The difference was statistically significant. The percentage of mast cells was increasing during the experiment duration. It was different from other cells populations which decreased after 168 hours. The MC and neutrophils were cell population which changed significantly after manipulations in peritoneal cavity. It is very probable that they play an important role in peritoneal adhesions formation.