We study optimal incentive contracts with multiple agents when performance evaluation is delegated to a reviewer. The reviewer may be biased in favor of the agents, but the degree of bias is unknown to the principal. We show that a contest, which is a contract in which the principal determines a set of prizes to be allocated to the agents, is optimal. By using a contest, the principal can commit to sustaining incentives despite the reviewer's potential leniency bias. The optimal effort profile can be uniquely implemented by an all-pay auction with a cap. Our analysis has implications for applications as diverse as the design of worker compensation, the awarding of research grants, and the allocation of foreign aid.