Warfarin is a cornerstone of oral anticoagulation for stroke prevention. Anticoagulation with warfarin in patients with atrial fibrillation is over twice as effective in secondary prevention of stroke as any other tested alternatives, including all other antithrombotic drugs or surgical interventions. General belief is that warfarin is capable of preventing 20 ischemic strokes for every hemorrhagic one it causes. However, warfarin is one of the most feared agents as a result of its woeful safety profile and difficulties in maintaining the proper daily dose. Recent research in pharmacogenetics predominantly focused on elucidating the influence of individual genetic predispositions to administered warfarin. Although the incorporation of genotype information improves the accuracy of adequate dose prediction, an improvement in anticoagulation control or a reduction in hemorrhagic complications has not been yet convincingly demonstrated. It is clear that identifying an individual patient's risk for hemorrhage on warfarin will require more broad clinical and genetic studies. Future research focused on patients with stroke should concentrate on defining the possible differences, especially focusing on predicting bleeding events in general and intracranial hemorrhages in particular. The purpose of this review is to summarize the existing evidence about pharmacogenetics of warfarin in general, especially focusing on stroke prevention.