 We will develop a nomogram for warfarin dosing that uses rapid turnaround genetic testing and monthly nomogram modification if necessary to achieve effective and safe warfarin induction and maintenance. More than 70 of the time, we will maintain warfarin naïve patients within the target therapeutic range. The percent of time in the therapeutic range will be analyzed beginning 2 weeks after initiation of warfarin. Analyses will be stratified by the indication for anticoagulation. 