35 patients with various phases of generalized purulent peritonitis were tested. The goals of this study were to define the colloid-oncotic pressure (COP) and the contents of its main ingredient--albumin, determine the significance of the COP studies for the diagnosis of edema of lungs in cases of purulent peritonitis, and the influence of fluid management and parenteral nutrition upon the COP index. The studies have shown a clear dependency of COP and albumin ratio upon the phase of peritonitis. The authors come to a conclusion that the definition of COP dynamics is one of the most reliable criteria that makes it possible to chart a correct program of fluid management and reduce the number of postinfusional complications.