OBJECTIVE: To perform pharmacoeconomical analysis of unfractionated heparin (UFH) versus dalteparin (D) for thrombosis prevention in patients with malignancies. METHODS: Randomized open pharmacoeconomical study included 99 patients after operative involvement for cancer of stomach or bowels: 50 in D group and 49 in UFH group. The efficiency of studied drugs was assessed by monitoring soluble fibrin monomeric complexes (SFMC) in blood serum that was considered to be a prognostic factor for thromboembolism. Costs included direct medical expenditures for hospital treatment from payer's perspective. RESULTS: Both drugs significantly reduced SFMC after operation, but patients in D group had significantly more expressed decrease in the level of SFMC, than in UFH group (ð=0.003). In UFH group vs D group costs for medicines per patient for period of treatment were significantly less (median cost 2849.4 rub. vs. 6066.4 rub.; ð=0.000) but costs for medical services were significantly higher (median 21,770.0 and 19,765.0 rub; ð=0.012), mainly because of more subcutaneous injections per day. CONCLUSION: D therapy leads to significantly more expressed decrease in SFMC level than UFH in cancer patients. At the same time costs per treatment are equal because high expenditures for drugs are compensated by less expenditures for injections. So D is a reasonable alternative to traditional UFH therapy.