The influence of the menopause on serum lipids and lipoproteins was examined longitudinally at 6-week intervals for 2-3 years in pre-menopausal women undergoing the menopause. Serum lipid and lipoprotein profiles were also examined cross-sectionally in 4 groups of pre-menopausal, perimenopausal and post-menopausal women, who were followed up longitudinally at 3-monthly examinations for 1-2 years. The results covering 1360 examinations and 270 woman-years are reported here. Serum concentrations of total cholesterol (P = 0.001), low-density-lipoprotein (LDL) cholesterol (P = 0.001) and triglycerides (P < 0.05) increased significantly as a consequence of the menopause and all increases occurred within 6 months of cessation of menstrual periods. High-density-lipoprotein (HDL) cholesterol decreased significantly (P < 0.05) as a consequence of the menopause, but the decline occurred gradually over the 2 years preceding cessation of menses. In addition to the menopausal changes, serum concentrations of total cholesterol and LDL-cholesterol increased gradually in the pre-menopausal and post-menopausal years, but were significantly related to biological age only in the pre-menopausal groups (P < 0.05). Serum triglycerides and HDL-cholesterol levels remained virtually unchanged in the pre-menopausal as well as the post-menopausal groups and were only influenced by the actual menopause. Serum lipids and lipoproteins are thus significantly altered as a consequence of the menopause. The result is a more atherogenic lipid profile which may partly explain the increased risk of cardiovascular disease observed in post-menopausal women. © 1990.