Insulin-dependent diabetes mellitus (IDDM) and eating disorders are relatively common among young women in North America. Their coexistence could lead to poor metabolic control and an increased risk of the microvascular complications of IDDM. We studied 91 young women with IDDM at base line and four to five years later to determine the prevalence and persistence of disordered eating behavior (on the basis of self-reported eating and weight-loss practices, including the intentional omission or underdosing of insulin to control weight) and the association of such eating disorders with metabolic control, diabetic retinopathy, and urinary albumin excretion. At base line, the mean age of the young women was 15+/-2 years and the duration of diabetes was 7+/-4 years. At base line, 26 of 91 young women (29 percent) had highly or moderately disordered eating behavior, which persisted in 16 (18 percent) and improved in 10 (11 percent). Of the 65 women with normal eating behavior at base line (71 percent), 14 (15 percent) had disordered eating at follow-up. Omission or underdosing of insulin lose weight was reported by 12 of 88 young women (14 percent) at base line and 30 (34 percent) at follow-up (P=0.003). At base line, the mean (+/-SD) hemoglobin A(1c) value was higher in the group with highly disordered eating behavior (11.1+/-1.2 percent) than in the groups whose eating behavior was moderately disordered (8.9+/-1.7 percent) or nondisordered (8.7+/-1.6 percent, P<0.001). Disordered eating at base line was associated with retinopathy four years later (P=0.004), when 86 percent of the young women with highly disordered eating behavior, 43 percent of those with moderately disordered eating behavior, and 24 percent of those with nondisordered eating behavior had retinopathy. Disordered eating behavior is common and persistent in young women with IDDM and is associated with impaired metabolic control and a higher risk of diabetic retinopathy.