A principal (e.g., the US government) contracts with a researcher with unknown costs (e.g., a vaccine developer) to conduct a costly experiment. This contracting problem has a novel feature that captures the difference between the form of an experiment and the strength of its results: researchers face a problem of information design rather than optimal effort. Using a novel comparative static for Bayesian persuasion settings, I characterize the optimal contract and show how experimentation is distorted by the need to screen researchers. Moreover, I show that there is no loss from contracting on the experiment’s result rather than the experiment itself.