This research compares the family environments of diabetic adolescents in good (HbA1c less than 10), fair (10 greater than or equal to HbA1c less than or equal to 14), and poor (HbA1c greater than 14) control. Fifty-eight adolescents diagnosed with type 1 diabetes and their parents (mothers) were independently assessed with structured interviews, the Moos Family Environment Scale, and adolescents also completed the Piers-Harris Children's 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 child's personality, physical well-being, schooling, and participation in activities away from home. These findings suggest a complex interplay between the diabetic adolescent's psychological and physical functioning, metabolic control, and the family environment.