In 163 patients with acute suppurations of lungs and pleura a substantial reduction of deformability of erythrocytes was established. The maximum increased rigidity of blood red cells was noted at the peak of the pyo-destructive process and postoperative period as well as in the complicated course of the postoperative period. The curative plasmapheresis, general hyperbaric oxygenation exert positive influence upon plastic properties of erythrocytes.