Interest organizations are hypothesized to strongly affect public policy, but the evidence that they do so is mixed. This article argues that one reason for the disparity is a gap between theory and research: theory suggests that information provided by interest organizations should strongly influence elected officials, but there is no systematic research on its impact. We examine a potentially important source of information for members of the U. S. Congress - testimony at committee hearings - to ascertain if it affects the enactment of policy proposals. The data, based on content analysis of almost 1,000 testimonies on a stratified random sample of policy proposals, describe who testifies, their arguments, and the evidence they provide. Supporters of a proposal emphasize the importance of the problem being addressed, while opponents claim the proposed policy will be ineffective and try to reframe the debate. Information - particularly information regarding policy effectiveness - does affect the likelihood that a policy proposal will be enacted.