Objective: To examine lipid parameters that are affected in women with insulin-dependent diabetes mellitus (IDDM) who engaged in disordered eating behaviours. Design: Randomized, unmatched. Setting: Tertiary care. Subjects: Ninety women (18±46 y) with IDDM. Interventions: Classi®cation of subjects based on severity of eating disorder: clinical (n 14), subclinical (n 13) and control (n 63). Blood was analysed for glycosylated haemoglobin (HbA 1c ) and serum for triglycerides and cholesterol. Carotenoid and tocopherol concentrations were analysed by high performance liquid chromatography (HPLC). Dietary intake was assessed by the National Cancer Institute food frequency questionnaire. Results: HbA 1c was signi®cantly increased im women demonstrating clinical and subclinical symptoms compared to control (10.4 AE 2.6, 10.0 AE 1.5 and 8.3 AE 1.6%, respectively, P`0.05). Triglyceride concentrations were signi®cantly increased in women with subclinical eating disorders compared to controls. In women who intentionally omitted or reduced insulin, triglyceride cholesterol and HbA 1c were signi®cantly increased compared to controls. Women with IDDM and eating disorders who exhibited bulimic behaviours consumed signi®cantly more energy, total fat and cholesterol compared to controls and women with eating disorders who were restrained eaters. Conclusion: While IDDM is known to perturb lipid metabolism, these data demonstrate that eating disorders, in combination with IDDM, results in additional alterations in lipid metabolism.