The potential of distance learning technology to deliver educational programs in which instruction and evaluation are of a consistent and high standard across multiple settings is hampered by a lack of instructional design models. In response, we developed the HEAL (Heuristic for Electronic Asynchronous Learning) model for designing online curricula. HEAL is based on the theories that learning is facilitated by independent problem solving, investigation, and discovery (heuristics); collaboration between students fosters learning; and the proven educational cycle of practice, feedback, and reflection is integral to the interrelated domains of skill development and personal awareness.(1) The HEAL model is defined by synergistic online learning activities integrated with real patient care. It is applicable to all medical education levels. We applied this innovative design template to an online curriculum that augments our conventional six-week third-year clerkship. Our students, who were placed in distant family physician offices, needed more interaction and learning from peers and faculty. The three elements of HEAL, and implementation in the "online clerkship," are: (1) Didactic modules teach and illustrate concepts. Students study modules (HTML pages) on management of diabetes (DM), and complete five modules on evidence-based medicine (EBM). They do EBM literature searches reviewed online by peers, faculty, and librarians, who provide feedback. (2) A problem-based case discussion promotes application of concepts from modules (horizontal curricular integration). Students view streamed video of a patient with a history suggestive of diabetes, review her medical chart online, and suggest evidence-based management in an asynchronous discussion group. The case progresses weekly to mimic 12 months of continuity of care. (3) A collaborative journal activity explores the results of applying elements one and two to real patients (vertical integration). Additional elements advance reflection, professionalism, and medical humanism. Participation in the journal discussion group, stimulated by online readings, enhances self-awareness, informs psychosocial aspects of element 2, and promotes generalization of learning objectives to real patients. We use BlackBoard software. Students log in two to three times per week. Faculty who are trained in online moderation facilitate the threaded discussion groups and provide feedback. Students in alternating clerkship blocks complete the online clerkship. Their performance is compared with that of students who complete a face-to-face diabetes curriculum, but no curriculum on EBM or medical humanism. After nearly a year (105 students), compared with the non-online group, students completing the online clerkship demonstrated greater gains in reported EBM skills from preto post-clerkship, larger increases in mean score (from pre to post) on a medical-humanism aptitude scale, and higher scores on a post-clerkship diabetes management assessment (all comparisons p <.05). The online clerkship will become a permanent part of our clerkship and we have begun to use HEAL to design other online courses, including continuing education courses.