PURPOSE: To determine the thromboprophylactic treatment pattern and occurrence of venous thromboembolism (VTE), major bleeding, and wound infections in patients undergoing total knee replacement (TKR) or total hip replacement (THR). METHODS: From te PHARMO database, all patients >/= 18 years hospitalized for TKR or THR between January 2003 and September 2008 were selected. Patients with pharmacy data up to 3 months after hospitalization were included in the study cohort. Duration and type of thromboprophylaxis were assessed. VTE, major bleeding, and wound infections were identified by hospitalizations. Regarding VTE, timing of event in relation to thromboprophylaxis was determined. RESULTS: The study population included 2930 patients with TKR, 5332 patients with THR without hip fracture, and 289 patients with THR and hip fracture. Mean duration of thromboprophylaxis was about 30 (+/- 20) days for all procedures, with low-molecular-weight heparin being the most frequently used drug. During 3 months of follow-up, 1% to 2% of patients were hospitalized for an event. The most observed event was wound infection (58%), followed by major bleeding (29%), and VTE (13%). For wound infection and major bleeding, median time after surgery was about 19 days.Median time between surgery and VTE was 24 days for TKR and 60 days for THR. Eighteen of 23 VTE occurred during thromboprophylaxis. CONCLUSIONS: Although patients are often treated for fewer days than recommended, thromboprophylaxis after TKR and THR inthe Netherlands is adequate. Only 5 of 23 VTE hospitalizations occurred off-treatment and might have been prevented. Furthermore, fewer than 1% of patients were hospitalized for bleeding.