Results of our own studies and literature data on the functional activities of neurohypophysis hormones, including arginine-vasopressin (AVP) and oxytocin (OX), as well as their modified forms and fragments, with respect to the parameters of the haemostasis system were analyzed in this review. Modification of the amino acid composition of the natural hormone was found to cause significant changes in its functional activities on the blood coagulation system. The intact molecule of the peptide is necessary for manifestation of the main effects of AVP and OX. The presence of the C-terminal glycylamide in the molecule determines the fibrinolytic effects of vasopressin, which are associated with an increase in the activity of the tissue plasminogen activator (t-PA). Peptides lacking this group have a more pronounced effect on procoagulant blood activity.