['The history of venous thromboembolism (VTE), and the rationale for thromboprophylaxis in surgical patients are well understood. The situation is less clear for acutely ill medical patients.', 'To compare the clinical presentation of VTE and clinical outcomes of immobile acutely ill medical patients with surgical patients.', 'RIETE (Registro Informatizado de la Enfermedad TromboEmbolica) is a Spanish registry of consecutively enrolled patients with objectively confirmed, symptomatic acute VTE. In this analysis, clinical characteristics of patients, details of anticoagulant therapy, and outcomes of all enrolled acutely ill medical patients with immobility >/= 4 days, and surgical patients are included.', 'Of 6160 patients enrolled up to December 2003, 756 (12%) were acutely ill medical patients with immobility >/= 4 days, and 884 (14%) were surgical patients who developed VTE within 2 months of surgical intervention. Only 28% of acutely ill medical patients had received thromboprophylaxis, compared with 67% of surgical patients. During the 3-month follow-up period, both fatal pulmonary embolism (PE) and fatal bleeding occurred more frequently in acutely ill medical patients. Immobility in acutely ill medical patients, cancer, and PE were associated with a significantly higher risk of fatal PE or bleeding.'] Is the outcome after treatment of venous thromboembolism different in surgical and acutely ill medical patients . Findings from the RIETE registry?