An intervention was developed to increase patient involvement in care. Using a treatment algorithm as a guide, patients were helped to read their medical record and coached to ask questions and negotiate medical decisions with their physicians during a 20-minute session before their regularly scheduled visit. In a randomized controlled trial we compared this intervention with a standard educational session of equal length in a clinic for patients with ulcer disease. Six to eight weeks after the trial, patients in the experimental group reported fewer limitations in physical and role-related activities (p less than 0.05), preferred a more active role in medical decision-making, and were as satisfied with their care as the control group. Analysis of audiotapes of physician-patient interactions showed that patients in the experimental group were twice as effective as control patients in obtaining information from physicians (p less than 0.05). Results of the intervention included increased involvement in the interaction with the physician, fewer limitations imposed by the disease on patients' functional ability, and increased preference for active involvement in medical decision-making.