Association of serum lipids with metabolic control and diet were studied in 72 young subjects with insulin-dependent diabetes mellitus (IDDM). Data on food consumption were collected by the 48-h recall method. Glycosylated haemoglobin (Hb) A1 was used as a measure of metabolic control. There were no differences between males and females in the mean values for serum total cholesterol (TC, 4.5 and 4.9 mmol/l, respectively), low density lipoprotein cholesterol (LDL-C, 2.7 and 3.0 mmol/l), high density lipoprotein cholesterol (HDL-C, 1.3 and 1.4 mmol/l), or serum triglycerides (TG, 1.1 and 1.0 mmol/l). Diabetic subjects who were in better metabolic control (HbA1 < 10.5%), when compared with those in poorer control (HbA1 > or = 10.5%) had lower TC and TG values and a higher HDL-C/TC ratio. HbA1 level and intake of saturated fatty acids were positively associated with serum TC and LDL-C values and explained 14% and 15% of the variation in TC and LDL-C, respectively. HbA1 level and insulin dose per kg of body weight were positively associated with serum TG values and explained 30% of the variation in TG. Serum TC and LDL-C levels of young subjects with IDDM could be lowered by improving their metabolic control and decreasing their saturated fatty acid intake.