Abstract: Health plans in the U.S. increasingly use cost-sharing to steer demand for prescription drugs. However, the effectiveness of these incentives depends both on physicians' price sensitivity and their knowledge of patient costs. We employ a moment inequality model to identify physician preferences without fully specifying their information. Applying this model to diabetes care, we find that physicians generally lack detailed price information and are more price sensitive than full-information models imply. We also identify substantial heterogeneity in preferences and information by physician training, suggesting a benefit from targeted information interventions.