Abstract Introduction Population-based evaluation on the incidence of postoperative venous thromboembolism (VTE) has not yet been reported for Asians receiving arthroplasty. In Taiwan, thromboprophylaxis was not commonly applied for patients. The population-based cohort study aimed to investigate the epidemiology, and to determine the risk factors VTE for patients receiving hip or knee replacement without pharmacological thromboprophylaxis in Taiwan. Materials and Methods We retrospectively acquired patients’ data from National Health Insurance databases representing more than 99% of about 23 million Taiwanese citizens. The primary outcome was the incidence of composite symptomatic VTE within 28days after receiving hip or knee replacement surgery. Results During 2002 to 2006, there were 114,026 patients undergoing hip (n=61,460) or knee (n=52,566) replacement surgery. The occurrence rate of overall postoperative VTE was 0.44%. The incidence of pulmonary embolism was four in 10,000 patients receiving hip replacement or seven in 10,000 individuals undergoing knee replacement. The weekly cumulative incidence of VTE was persistently rising up to 28days after surgery. Dramatic increase in risk of post-surgical VTE was associated with prior disease history of PE (p<0.001 for hip replacement, p=0.01 for knee replacement) or DVT (p=0.004 for hip replacement, p<0.001 for knee replacement). Prior claim of congestive heart failure was an independent risk factor associated with patients receiving knee arthroplasty (p=0.01). Conclusion Life-threatening PE occurred and increased cumulatively up to 28days after hip or knee arthroplasty in Asians. Proper prophylaxis for patients with the exposure of high risks needs to be scrutinized.