Hospitalized medical patients are at risk of deep-vein thrombosis (DVT) and pulmonary embolism (PE). We evaluated inpatient and postdischarge DVT/PE and thromboprophylaxis rates in US medical patients, using patient admissions from January 2005 to November 2007 in the Premier Perspective™-i3 Pharma Informatics database. Among 15 721 patients with cancer, congestive heart failure, severe lung disease, and infectious disease, 39.0% received inpatient thromboprophylaxis, with the highest rate in patients with cancer (51.9%). In all, 3.4% received outpatient pharmacological prophylaxis. Mean ± SD prophylaxis duration was 2.2 ± 5.7 days. Overall, 3.0% of inpatients had symptomatic DVT/PE, and an additional 1.1% of patients were rehospitalized for DVT/PE or treated in the outpatient setting. Patients with infectious disease had the highest rate of DVT/PE (4.6%). Inpatient DVT/PE and prophylaxis rates of the different medical conditions had a negative correlation (R(2) = 0.72). This analysis demonstrates the burden of DVT/PE and highlights the underuse of thromboprophylaxis across the continuum of care.