Introduction. Heparins are one of the most frequently prescribed drugs in the world due to PE prophylaxis and treatment, just as heparin prevention “bridge” often used perioperatively in those constantly receiving oral anticoagulants. Heparin-induced thrombocytopenia (HIT) is an immune-mediated life-threatening complication, accompanied by paradoxical thrombosis and high mortality rate (up to 30%). Immunodiagnostics of HIT is rather expensive. Existing scales of probability of HIT (for coronary shunting; expert Scale HEP and Scale "4-x T") are too difficult, have low specificity and lead to overdiagnosis. Our aim was to determine the incidence of HIT in multidisciplinary hospital before and after implementation of the original diagnostic "Rule" - “100-5-100” (that means “decrease in platelet counts less than 100×109/L on the 5-th day of Heparins use or within 100 days of their previous use”) and new Algorithm of HIT treatment (including Fondaparinux sodium as alternative anticoagulant). Patients, materials and methods. At the beginning of 2014 the stuff have been informed in original "Rule" (see above) and Algorithm. Patiens were studied by electronic medical Records before the implementation of the "Rule" and Algorithm ("control group" hospitalized from 01.01.2013 to 31.01.2013) and after its implementation ("comparison group" - those hospitalized from 01.01.2014 to 31.12.2015). In some cases HIT diagnosis was confirmed by a method of immunoturbidimetry (ACL TOP 700). Results. We identified severe thrombocytopenia in 5018 blood samples obtained in 950 patients (1.3% of admissions). 382 of them received Heparins (40.2%). The implementation of "Rule" and Algorithm was accompanied by a decrease in the HIT incidence in 2014-2015 about 2 times compared to 2013. That was particularly noticeable in the departments of cardiac surgery, traumatology, urology and vascular surgery, as well as in intensive care units (ICU). There was a significant decrease in mortality rates in ICU patients from 26.1% in 2013 to 9.8% in 2014 (p<0.05) and 7.5% in 2015 (p<0.05). No noticeable dynamics in patients with "non-heparin" thrombocytopenia was observed. Conclusion. The use of the original "Rule" of HIT diagnostics and treatment Algorithm contributed to a decrease in the HIT incidence and the frequency of complicated HIT, which was manifested by a significant decrease in the number of such cases in the ICU with a statistically meaningful reduction in mortality rates. Sodium fondaparinux is an affordable, effective and safe drug of choice in the treatment of HIT.