Intranasal administration of Semax, peptide Pro-Gly-Pro, and a mixture of peptides Pro-Gly+Gly-Pro to rats for 5 days enhanced anticoagulant and fibrinolytic potential of the plasma (total fibrinolytic activity and plasmin and plasminogen activator activities) and decreased antiplasmin concentration. Semax and Pro-Gly-Pro decreased the weight of thrombi during experimental thrombosis.