Women with diabetes experience much greater relative risks of coronary heart disease (CHD) compared with the nondiabetic population than do men with diabetes. In type 2 diabetes, much of the greater elevation in risk in women is explained by a more adverse pattern of known CHD risk factors. In type 1 diabetes the picture is less clear, but current evidence suggests that a cardioprotective lipid profile is found in type 1 diabetic men, thus reducing the effect of diabetes on CHD, but that in women this is not the case. Also, in type 1 diabetic women there is some evidence of altered body fat distribution and a greater elevation in blood pressure. Whether these reflect a greater degree of insulin resistance in type 1 women, and what the origin of this might be, remains controversial. The practical consequence is that clinicians need to be aware that the usual cardioprotective effect of sex does not apply in diabetic women and that risk factor intervention is needed at an early age.