Between 2000 and 2004, we developed a computer generated alert system for VTE prophylaxis and tested it in a large randomized controlled trial at Brigham and Women's Hospital. The system was linked to the patient database, identifying patients at high risk for VTE (defined as ≥ 4 score points and shown in Table 1) who were not receiving prophylaxis. High-risk patients not receiving VTE prophylaxis were randomized to an intervention group in which their physicians received an electronic alert or a control group in which physicians were not alerted. Patients in the intervention group experienced a 41% reduction in the incidence of symptomatic VTE events within 90 days, without an increase in the risk of major or minor bleeding. However, prophylactic measures were prescribed for only 33.5% of the patients in the intervention group. For the remaining patients (66.5%), we were surprised that physicians declined to implement the suggested intervention, initiation of VTE prophylaxis.