Mast cells and vascular permeability were examined in experimental aseptic peritonitis induced by intraperitoneal injection of starch into rats. It was established that derangement of vascular permeability in the inflammatory focus was consequent on degranulation of mast cells and release of inflammatory mediators. The model of the inflammation suggested enables the local focus to be created, with no mast cells seen for a long period of time (at least for 3 weeks).