Serum lipid profiles were studied in 167 healthy fertile Singaporean women, aged between 18 and 40 and comprising 114 Chinese, 28 Malays and 25 Indians. Parity or ethnic differences did not affect lipid concentrations. Except for triglycerides which showed a decreasing trend, there was no significant variation in lipid concentrations with age. However, all lipid concentrations except HDL cholesterol (which decreased) appeared to increase with body mass index. Compared with other populations, these Singaporean women appeared to have higher mean concentrations of total cholesterol and lower mean concentrations of HDL cholesterol. The possibility that these differences could have contributed to the increasing incidence of coronary heart disease in Singapore is discussed.