Coronary heart disease (CHD) is the most common cause of premature death in diabetes. Hypercholesterolaemia occurs in diabetes with about the same frequency as in the general population, but it confers a greater risk of CHD in diabetes. Hypertriglyceridaemia and low serum high density lipoprotein (HDL) cholesterol levels are more common in diabetes, particularly non-insulin-dependent diabetes. Nephropathy increases the severity of dyslipoproteinaemia. There remains a reluctance to apply the results of cholesterol-lowering trials to diabetes. No trial has been specifically in diabetes, but this should not constrain the treatment of diabetic patients at clearly high CHD risk. It is suggested that fasting lipids should be measured in all diabetic patients aged less than 70 years with established CHD or whose non-fasting cholesterol is >6.00 mmol I(-1) or triglycerides >3.00 mmol I(-1). For those with raised lipids glycaemic control should be improved, if possible, and dietary therapy aimed at a decrease in fat intake, particularly saturated fat, and weight reduction in the obese. Lipid-lowering drugs are required in patients with CHD and serum cholesterol >5.5 mmol I(-1) with the aim of decreasing non-HDL to <4.00 mmol I(-1). In patients without CHD lipid-lowering drugs should be considered when serum cholesterol exceeds 6.5 mmol I(-1) and the risk of CHD is greater than 20 % over the next 10 years. There is no evidence that pursuing this policy beyond the age of 70 years is beneficial. Diabetic women with dyslipoproteinaemia should, however, be treated in the same way as men. The knowledge that hypertriglyceridaemia and low serum HDL cholesterol are present helps in the assessment of CHD risk and the choice of medication to decrease non-HDL cholesterol, but there is no evidence that their treatment in the absence of raised cholesterol is of benefit.