This research compares the family environments of diabetic adolescents in good (HbA1c < 10), fair (10 ≥ HbA1c ≤ 14), and poor (HbA1c > 14) control. Fifty-eight adolescents diagnosed with type I diabetes and their parents (mothers) were independently assessed with structured interviews, the Moos Family Environment Scale, and adolescents also completed the Piers-Harris Children9s Self-Concept Scale. As compared with adolescents in poor control, those in good control reported fewer diabetes-related symptoms and had less anxiety and a more positive self-concept. Well-controlled youths also reported more cohesion and less conflict among family members. More parents of well-controlled youths stated that family members were encouraged to behave independently. In addition, more parents of poorly controlled adolescents believed that diabetes had negatively affected the child9s personality, physical well-being, schooling, and participation in activities away from home. These findings suggest a complex interplay between the diabetic adolescent9s psychological and physical functioning, metabolic control, and the family environment.