Sex hormone deficiency is associated with increased coronary heart disease (CHD) risk in women. We measured fasting serum lipids and lipoprotein concentrations in a group of 542 healthy non-obese pre- and postmenopausal women (aged 18-70 years). Ageing was associated with increased concentrations of total cholesterol, low density lipoprotein (LDL) cholesterol, high density lipoprotein subfraction 3 (HDL3) cholesterol and triglycerides, and decreased concentrations of high density lipoprotein subfraction 2 (HDL2) cholesterol. Body mass index (BMI) was related positively to concentrations of total and LDL cholesterol. Postmenopausal women had significantly higher concentrations of total cholesterol (P < 0.001), triglycerides (P < 0.005), LDL cholesterol (P < 0.001) and high density lipoprotein subfraction 3 (HDL3) cholesterol (P < 0.001), whilst those of HDL and HDL2 cholesterol were significantly lower (P < 0.001). These differences were independent of age, BMI and other potential confounding variables. We conclude that the menopause is associated with potentially adverse changes in lipids and lipoproteins, independent of any effects of ageing. These changes may in part explain the increased incidence of coronary heart disease seen in postmenopausal women.