Purpose: A retrospective database analysis was conducted to determine the extent to which the American College of Chest Physicians (ACCP) guidelines for VTE prophylaxis are followed after total hip replacement (THR) and total knee replacement (TKR) and evaluate the incidence of VTE for patients receiving and not receiving prophylaxis according to ACCP guidelines (‘ACCP’ and ‘non-ACCP’, respectively). Method: A claims database associated with a large US health plan was linked to the Premier database, which provides details of in-patient medication use. Patients ≥18 years undergoing TKR/THR and enrolled in the health plan 90 days before and 90 days following discharge from hospitalization (or until death) were included. Patients were considered to have received ACCP-guideline prophylaxis if they: received LMWH, fondaparinux, or VKA following surgery initiated prophylaxis within one day of surgery (for THR patients) and were prescribed prophylaxis for a minimum of ten days, or until the occurrence of major bleeding, VTE, or death. In addition, the number of DVTs and PEs occurring in ACCP and non-ACCP patients was recorded. Results: Of the 30,644 eligible patients from the health plan, 3,497 patients were linked to the in-patient database. Except for geographic indicators, there were no significant differences in demographics or baseline co-morbidities between those included and excluded from the final study sample. Of the 3,497 linked patients, 1,395 (40%) received ACCP prophylaxis. The number of DVTs occurring in the ACCP and non-ACCP groups were 28 (2.01%) and 79 (3.76%), suggesting that non-ACCP patients were almost twice as likely as ACCP patients to have a DVT (p=0.0521). The number of PEs occurring in the ACCP and non-ACCP groups were 2 (0.14%) and 25 (1.19%), respectively, suggesting that non-ACCP patients were 8.5 times more likely than ACCP patients to experience a PE (p Conclusion: This study offers a unique perspective on ‘real-world’ prophylaxis patterns and clinical outcomes in THR/TKR patients. It suggests that 40% of patients received ACCP prophylaxis and that patients not receiving ACCP prophylaxis were almost twice as likely to have a DVT and more than eight times as likely to experience a PE.