This study investigated the impact of patients' participation on physicians' information provision during a primary care medical interview. When communicating with high-participation patients, physicians provided significantly more information overall, more information in response to patients' questions, and volunteered more information than when interacting with low-participation patients. The most significant differences with respect to volunteered information involved communication about treatment and tests or procedures. These results were interpreted to suggest that high-participation patients' communication style promotes better alignment of patients' and physicians' goals and agendas. Overall, the results suggest that patients' style of participation during a medical interview significantly influenced the extent and type of information physicians provided. Given that patients' biggest complaint about physicians often is a lack of desired information, this study has important implications for physician-patient communication.