Patients are using the Internet for access to standardized health information in ever-growing numbers. Although increased access to health information can be helpful, the quality of information varies widely. All too often, the information retrieved is incomplete, inaccurate, or inappropriate. An interdisciplinary team of clinicians, librarians, software engineers, and multimedia designers developed an online patient education system that enables clinicians to "prescribe" tailored, evidence-based health information. The system provides access to text and video that patients can adapt for language, vision, and hearing preferences. Usability testing was conducted with eight patients in a usability laboratory using the "think-aloud" method, surveys, and interviews. Results indicated that patients were highly satisfied and that the site has the potential to become a valuable resource in disease management. Patients made several recommendations regarding system appearance, function, and content that will have application for other groups developing online patient education systems.