Background. A major challenge in surgery is the integration of evidence-based medicine and patient autonomy. The authors present a randomized trial studying the effect of an individualized evidence-based brochure (IB) on patients' autonomous behavior, patients' ideals of autonomy, and quality of life. Method. Patients with an asymptomatic abdominal aneurysm and their surgeon were randomized to receive a general brochure (GB) or an IB presenting survival information and a ranking of the treatment strategies. Before and after receiving the brochure, patients filled out questionnaires on their behavior during the consultation, ideals of patient autonomy, and quality of life. Surgeons answered a short checklist evaluating the consultation. Results. One hundred patients participated, 49 in the intervention, 51 in the control group. The IB group had a better understanding of important issues in the treatment decision, had prepared more questions, and was less satisfied with the duration of the consultation. Their impression that the surgeon perceived them more as a medical problem than a patient with a problem increased. They agreed less with the surgeon's advice and lost some of their belief in ''the doctor knows best.'' Beforehand, the IB group had a stronger preference for patient-based decisions, but afterward they displayed more surgeon-based decisions. No effects were seen on patients' quality of life. Conclusions. Individualized evidence-based information stimulated patients' active involvement but in the context of our study led to less patient-based decisions. Patient-made decisions and patient autonomy should, however, not be equated.