Risk-sharing agreements, under which payers and pharmaceutical manufacturers agree to link payment for drugs to health outcomes achieved, rather than the volume of products used, offer an appealing payment model for pharmaceuticals. Although such agreements have been widely touted, the experience to date mainly demonstrates how hard they are to implement. Barriers include high implementation costs, measurement challenges, and the absence of a suitable data infrastructure. Risk-sharing arrangements could gain traction in the United States as payers and product manufacturers acquire experience with the concept and as measurement techniques and information systems improve. For the foreseeable future, they are likely to remain the exception as drug companies pursue payment models unconnected to data collection or performance assessment.