OBJECTIVES: Prophylactic dalteparin reduces the incidence of deep venous thrombosis (DVT) after hip replacement. The aim of this analysis is to perform a pharmacoeconomic evaluation of prolonged (35 day) versus short (7 day) prophylaxis with dalteparin for this indication. METHODS: A cost-effectiveness analysis was carried out by building a decision analytic model. Effectiveness data were taken from a meta-analysis of all clinical trials (CT) of dalteparin in prolonged prophylaxis after hip replacement. After pooling and analyzing all CT found, the incidence of DVT was 6.1 % with a prolonged prophylaxis and 15.1 % when using a short prophylaxis. Health care resources utilization with dalteparin was taken from the aforementioned meta-analysis and a local expert panel. Only direct medical costs were included in the model (drug acquisition, length of hospital stay, diagnostic procedures and treatment of DVT cases). Drug acquisition cost data were obtained from official sources while the rest of the data were taken from a national Health care cost database. The perspective selected for this analysis was the National Health Service and the time horizon chosen was 35 days, being the maximum time that patients received dalteparin as prophylaxis. RESULTS: In two hypothetical cohorts of 500 patients, 424 patients reported no DVT cases in the prolonged prophylaxis group resulting in a cost/patient free of DVT of € 370 whilst 469 patients in the short prophylaxis group reported no DVT thereby giving a cost/patient free of DVT of € 611. CONCLUSION: This pharmacoeconomic analysis demonstrates that prolonged prophylaxis with dalteparin is a more efficient alternative than short prophylaxis, as it presents better clinical results with lower associated costs and a lower cost/effectiveness ratio.