Because the costs of anticoagulation therapy are substantial and the difference between the risks and benefits of this therapy are often narrow, economic analyses are particularly valuable when weighing anticoagulation options. Economic analyses to date suggest that anticoagulation is most effective and results in the greatest cost savings when applied to populations at highest risk for thrombotic events. They also suggest that in situations where a more costly anticoagulant agent is available, that agent is cost-effective only if it is clearly more efficacious or if it substantially reduces costs in other areas, such as hospitalization. These principles should guide clinicians' choices of anticoagulation strategies.