Behavioral economics may offer a powerful tool for improving patient enrollment in clinical trials, argue Eric VanEpps, Kevin Volpp, and Scott Halpern in this Focus. Drawing insights from economics and psychology, the authors propose interventions, or "nudges," to influence patients' decisions to enroll in a trial. For example, one strategy for resolving anxiety about enrolling is to convey the number of other participants when providing information about the trial, a tactic that leverages a "safety in numbers" mentality. Default or automatic enrollment in low-risk trials, such as for a smoking cessation program, may combat inertia by requiring patients to explicitly "opt out." Financial and social incentives can also make participation seem more attractive, from non-monetary prizes to sharing trial results with the patients. While enrollment nudges may be viewed to be in conflict with informed consent, they do not "coerce" patients to participate, the authors argue. If successfully tested in behavioral labs, such nudges may offer a new approach for using behavioral economics to advance public health.