OBJECTIVES: Antithrombotic agents have been recommended to prevent venous thromboembolism (VTE) after major orthopedic surgeries, yet neither effectiveness evidence nor guidance for prophylactic antithrombotic agents is available in Taiwan. This study aims to evaluate current utilization of prophylactic antithrombotic agents after total hip and knee replacement (THR/TKR). METHODS: This retrospective cohort study used a Taiwanese National Health Insurance dataset including 1,000,000 beneficiaries randomly sampled in 2005 from nationwide population and followed longitudinally from 1995 to 2008. Adults hospitalized for THR or TKR were identified by procedure codes from April 2003 to June 2008. Patients with VTE, bleeding events, or antithrombotic prescriptions within 90 days pre-admission were excluded. Eligible patients’ characteristics, medication during operation, and antithrombotic prescription up to 30 days post-admission were collected, presented in descriptive statistics, and stratified by different operations. RESULTS: Of all, 1026 THR (41.03% women) and 2401 TKR (75.51% women) were identified, with mean age of 56.36 ±14.50 and 69.07±8.28 years, and average length of stay for 9.41±4.45 and 9.17±4.55 days, respectively. Most procedures were conducted at medical centers (45.52% and 37.57%). The most frequent diagnoses for THR are avascular necrosis (45.22%) and osteoarthritis (44.05%); while for TKR is osteoarthritis (96.42%). Only 40 THR (3.90%) and 160 TKR (6.66%) had ever been prescribed antithrombotic agents after surgeries, and mostly used aspirin alone (18 THR and 95 TKR). CONCLUSIONS: According to this nationwide individual patient dataset, antithrombotic agents are not commonly used after THR and TKR in Taiwan, but aspirin is the most frequently prescribed of all. These findings deviate from the recommendations of current international guidelines. To establish Taiwanese own guidance, it is necessary to further investigate the effectiveness and safety of prophylactic antithrombotic agents after THR and TKR, and explore the influences of reimbursement policy and genetic factors on these outcomes.