The manuscript describes experiments designed to examine factors that influence erythrocytes aggregation within the blood of burn patients. Results showed that the rate and degree of erythrocytes aggregation increased significantly in burn patients, and what is especially unfavorable for microcirculation, erythrocytes disaggregation decreased. We show that normalization of blood plasma contents completely restores erythrocytes aggregation and disaggregation of burn patients. The rate and degree of aggregation was also increased as the fibrinogen concentration increased. It is found that fibrinogen-induced aggregation of erythrocytes is accompanied by "saturation" effect. The aggregation was not affected by monoclonal antibodies against platelet GPIIb/IIIa receptors. The level of oxidized fibrinogen in blood plasma of burn patients increased by about two fold. However, correlation between the level of oxidized fibrinogen and erythrocytes aggregation was not found. The level of medium molecular peptides increased sharply in blood plasma from burn patients. This increase was accompanied by a dose-dependent increase in erythrocytes aggregation. Based on these results the authors conclude that in burn patients erythrocytes aggregation is affected by changes in the contents of blood plasma, specifically fibrinogen and the product of its transformation - fibrin fibrin monomer.