Serum lipids and lipoproteins were assessed after treatment with 2 mg of oestradiol valerate (E2V) and 10 micrograms of ethinyl oestreadiol (EE) in a group of 24 oophorectomised women in a study with an open cross-over design. E2V in this oral dose was quite inert in its effect on lipoprotein lipids. Ten micrograms of EE is a dose which in most women is sufficient to alleviate post-menopausal vasomotor symptoms. However, this low dose of EE increased serum triglycerides as a result of increased levels in the ultracentrifugally isolated lipoprotein fractions. Increased levels of serum and lipoprotein triglycerides are considered cardiovascular risk factors in women.