Comparative effectiveness research generates evidence that helps consumers, clinicians, purchasers, and policy makers make better decisions about health care. Capturing the patient's perspective is central to this research because it provides a complete picture of treatment impact. This can be done with standardized questionnaires that ask patients to report on their functioning, well-being, symptoms, and satisfaction with care. These data, however, are not collected routinely in either clinical research or practice. Strategies and incentives to link patient-reported outcomes to data from conventional sources--including clinical research, electronic health records, and administrative data--will accelerate the development of useful evidence.