Аннотация:Abstract : Objective: To study the generation of thrombin in COVID-19 patients with thrombophilia against the background of ongoing therapy and in the recovery period. Materials and methods COVID-19 patients (n=14) with hereditary thrombophilia (FV and/or FII gene) – Group A, Group B (n=31) - with AT deficiency <60%, and/or PC <50%, and/or PS <55% and/or aPL were assessed for: thrombin generation (AUC, %) and concentration (Cmax, %). Results: COVID-19-associated prothrombotic condition associated with the severity of the disease and prognosis for patients. In COVID-19 patients, it is necessary to determine the generation of thrombin as the key protein in the regulation of hemostatic balance since the presence of thrombophilia can result in the resistance to anticoagulant therapy and increase the risk of thrombosis. Study of 45 hospitalized COVID-19 patients both during the acute phase (point 1) and recovery (point 2): Group A (n=14) hereditary thrombophilia (polymorphism of the Factor V (FV)) G1691A (Leiden) and/or FII G20210A gene); Group B (n=31) acquired thrombophilia (antithrombin (AT) deficiency <60%, and/or protein C (PC) <50%, and/or protein S (PS) <55%, and/or persistence of criteria antiphospholipid antibodies (aPL). Determination of the endogenous potential of thrombin was effected in citrate plasma samples by using a SIEMENS BCS XP coagulometer (Germany, Siemens-Healthcare Diagnostics), with the help of the kit - ETP "INNOVATION" (Siemens, Germany). The Mann-Whitney test aimed at assessing differences in the groups, while the McNemar test was to compare related data in one of the groups. The differences between the statistical values were considered statistically significant at a confidence level of p <0.05. The area under the curve (AUC) with the corresponding sensitivity (Se) and specificity (Sp) was considered appropriate for the adjusted regression model. In Group A, thrombin generation (AUC, 105% (101.1%-110.9%)) was higher than in Group B (AUC, 88% (83%-102%)) during the acute phase (P=0.0412), exceeding the reference interval at both points. Cmax in the groups was identical but increased progressively in patients of Group B – 108% (97.9%-120.6%) in point 2 (P=0.0407). COVID-19 patients with hereditary thrombophilia have higher thrombin levels, both during the acute phase and recovery period, despite ongoing anticoagulant therapy. Conclusions: The thrombin generation test can be used for COVID-19 patients with hereditary thrombophilia to monitor the thrombogenic potential of the hemostasis system and resistance to anticoagulant therapy. The work was carried out within the framework of the state task №121020500102-4. Keywords : COVID-19, thrombin generation, thrombophilia, hemostasis