Eligible subjects will be enrolled in one of the 4 arms of the RCT and followed for 6 months, with the primary outcome of out-of-range INRs. Subjects will be given a Med-eMonitor to connect to their home phone line. For all subjects, these will be used to measure daily adherence. Subjects in the incentive group will be eligible for a daily lottery prize only if, prior to the lottery being resolved, their adherence device has registered adherence to their prescribed warfarin regimen. Subjects in the MM group will have the reminder/feedback features of the Med-eMonitor turned on to provide reminders to take their warfarin as prescribed and standardized messages that will be used to provide feedback in response to their adherence. Subjects in the combined group will be exposed to both the lottery and the activated Med-eMonitor. This trial is a randomized controlled trial.