Diagnosed patients with atrial fibrillation, pulmonary embolism, or deep venous thrombosis requiring warfarin therapy will be consented and a tube of blood for DNA analysis will be drawn. The clinician dosing group will not be eligible to obtain the pharmacogenetic results and the algorithm group will have their warfarin pharmacogenetic SNPs performed and integrated into the algorithm and the warfarin dose will be calculated. Outcomes of patients receiving both methods will be gathered and statistically analyzed.