This research explores the question of what role medical family therapists play on a health care team when working with serious pediatric illness. Seven participants from three different health care settings were interviewed. Results were organized within the ecological systems framework (Bronfenbrenner, 1979) according to the various ways participants became a part of the family's illness experience. Participants identified roles directly with the family, with the health care team, and within the larger health care system. Clinical implications are identified concerning the preparation of the health care system for the continued growth and evolution of the field of medical family therapy.