Adults with developmental disabilities receive most of their health care from family physicians, yet little is known of the development of the patient-physician relationship in this population. This qualitative study used a grounded theory approach to describe the development of this relationship between adult patients with severe or profound developmental disabilities and their family physicians. Semi-structured interviews were conducted with 13 caregivers and 15 family physicians of these patients. The recognition of the patient’s vulnerabilities was a common starting point. Caregivers and patients approached the patient-physician relationship as one unit with the person they cared for as part of the process of protecting them, before allowing the relationship to develop along different trajectories. Family physicians described a mutual process of acceptance—of the patient as a human being, and of the physician by the patient. Greater awareness of these processes of relationship development may improve health care delivery for patients with developmental disabilities