BACKGROUND: The risk of coronary artery disease increases in women after menopause. This increased risk may be associated with alterations in the lipid profile characterized by changes in LDL particle size and buoyancy. Characterization of lipoprotein levels and LDL buoyancy across the stages of the menopausal transition has yet to be reported. METHODS: Plasma lipoprotein concentrations, LDL buoyancy, and body mass index (BMI) were studied cross-sectionally in five groups of women: premenopausal women (n = 42), women in early menopausal transition (n = 35), middle menopausal transition (n = 19), late menopausal transition (n = 20), and postmenopausal women (n = 14). No women were taking estrogen. RESULTS: The postmenopausal women had significantly higher low-density lipoprotein cholesterol (LDL-C) and total cholesterol than premenopausal women (P < 0.05). LDL-C and Apo B was significantly higher in women in the late menopausal transition compared to premenopausal women (P < 0.05). All women in the menopausal transition and postmenopause had significantly more dense LDL than premenopausal women (P < 0.05). Multiple regression analysis revealed that the change in LDL buoyancy associated with the menopausal transition period could be explained by changes in triglyceride and HDL-C, related to changes in body mass index. CONCLUSIONS: These data suggest that the menopausal transition is associated with more dense LDL and higher LDL-C levels in comparison to premenopausal women. It appears that whereas LDL-C may change late in the menopausal transition, the production of denser LDL particles appears early in the menopausal transition, both acting to worsen the lipoprotein profile. Increased triglyceride and decreased HDL appeared to account for the shift toward small, dense LDL, presumably related to increased BMI. The change in LDL density may contribute to the higher incidence of atherosclerosis in postmenopausal women.