Introduction: Classic non-fractioned heparin is used for years in the therapy of DVT. Fractioned, i.e.low molecular weight heparins (LMW) are increasingly used in the last two decades. There are a number of articles that LMW heparins are more safe in use, with the same or better efficiency. Objectives: We want to compare efficiancy of three types of heparin that we use in our daily work: non-fractioned heparin, and LMWs heparins - reviparin (Clivarin-Knoll) and enoxaparin (Clexane Rhone Poulenc). Methods and Material: We examined clinical efficiancy of three types of heparin in patients with DVT treated in our clinic in period 12/1999-12/2000. Total count of patients was 88 (M 47, F 41). Average age was 55 with SD 14,99. We treated 47 patients (53,4%) with non-fractioned heparin, 30 patients (34,1%) with reviparin, and 11 patients (12,5%) with enoxaparin. We have assess clinical effect, which was scored as bad, moderately improved and good. We have also analysed efficiancy of the three types of heparin regarding localisation of thrombosis. Results: Efficiancy of non-fractioned heparin was in 14,84 % of cases scored as bad, 29,68% as moderately improoved and in 57,24 % of cases as good. Efficiancy of reviparin was in 23,31 % of cases scored as bad, 29,97 % as moderately improoved and in 46,2% of cases as good. Efficiancy of enoxaparin was in 9,1% of cases scored as bad, 54,3% as moderately improoved and in 36,5% of cases as good. Conclusion: We have found that non-fractioned heparin had the best overall effect, although our group of patients treated with enoxaparin was too small to be definitely compared with other two groups. In no group we had maior bleeding complications.