Thirty-one patients with acute general peritonitis were studied. Lectin (LPM) demonstrated an additional peak on kinetic curves of erythrocytic osmolysis in patients with acute general peritonitis. Deformity of erythrocytes had a tendency to decrease (p > 0.05), but in the presence of LPM this difference increased sharply (p < 0.001). On day 7 after surgery in case of a favorable outcome the peak decreased or disappeared, deformity of erythrocytes also disappeared. It is important for diagnosis and prognosis.