OBJECTIVES: The purpose of this study was to evaluate the relative efficacy and safety of dalteparin against anticoagulant therapies in patients with: cancer, medical patients at risk of VTE, total hip replacement, and acute myocardial infarction(AMI). METHODS: A meta-analysis was performed with randomized clinical trials(RCT) where anticoagulant therapies were used to prevent or treat VTE. Effectiveness was assessed with the reduction in pulmonary thromboembolism(PE) and deep vein thrombosis(DVT) events; safety with the frequency and type of adverse events(AE). RCT were searched in December 2008 in Medline, EMBASE and the Cochrane Collaboration. Two independent reviewers identified the abstracts, selected the full articles and extracted data. Odds ratios and weighted means differences were calculated. Random effects models were employed in the analyses. RESULTS: From 2,539 abstracts, we obtained 91 RCT, 23 were excluded (unacceptable designs, insufficient outcome data) leaving 68. Dalteparin(2500-7500IU/day) was compared against unfractioned heparin, enoxaparin, warfarin, nadroparin, fondaparinux, aspirin and placebo. In patients with AMI, dalteparin showed to be effective in diminishing new infarctions and death (OR 0.66; 95%CI 0.33-0.99) or revascularizations (OR 0.76; 0.57-1.01). In total hip replacement patients, dalteparin showed reduction in DVT (OR 0.47; 0.38–0.60) but not in PE (OR: 0.45; 0.09–2.39). In comparison to placebo, the number of deaths were lower (OR 0.14; 0.02–1.27). In patients with VTE no statistical differences were found against competing alternatives, as well as in thromboembolism, thrombosis progression and death. Finally, in cancer patients, dalteparin showed to be effective in diminishing DVT(OR 0.39; 0.22–0.68) but not differences in reducing mortality (OR 0.92; 0.73–1.17); major bleeding(OR 1.20; 0.48–2.98) or minor bleeding (OR 0.87; 0.41–1.83). CONCLUSIONS: Dalteparin is an effective low-molecular-weight heparin in the prevention and treatment of VTE in surgery and non surgery patients, not showing higher AE than unfractioned heparin or other recommended therapies.