The optimal means of initiating warfarin therapy for acute venous thromboembolism in the outpatient setting remains controversial. We have previously demonstrated the efficacy of a 10 mg initiation nomogram in a randomized controlled trial; however, some clinicians remain reluctant to use this nomogram due to a fear of potential increased bleeding. To review the safety and efficacy of a 10 mg warfarin nomogram we conducted a retrospective cohort study of patients prospectively treated for venous thromboembolism according to a 10 mg nomogram in an outpatient thrombosis clinic. All patients received standard treatment with low molecular weight heparin for 5 to 7 days and warfarin for at least 3 months. Four-hundred and fourteen patients were included in the analysis, of whom 295 (71%) fully adhered to the nomogram. In the whole cohort, 8 patients (1.9%) experienced recurrent thrombosis, 4 (0.97%) suffered a major bleeding event, and 3 (0.72%) suffered a minor bleeding event. There were no deaths related to thrombosis or bleeding. Four patients (0.97%) died from unrelated causes. Twenty-two (5.3%) patients experienced an INR > or =5.0 in the first 8 days of therapy, and none of these patients experienced a bleeding event. Eighty-four percent of patients achieved a therapeutic INR by day 5. In outpatients, a 10 mg nomogram results in timely achievement of a therapeutic INR with an acceptable incidence of bleeding and recurrent thromboembolism.