The evolution of bone mass across menopause as well as the factors related to bone loss were studied in 141 women already assessed 10 years ago while in premenopause. Bone density of the lumbar spine was measured by dual photon absorptiometry. Nutrient intakes, lifestyle habits, data on menopause, and hormone replacement therapy were obtained by questionnaires. Present bone density was related significantly to past and current calcium intake, current vitamin D intake, and leisure physical activity level, as well as bone density measured in premenopause. Average bone loss was related to time elapsed without estrogens, age at menopause and present age, as well as serum levels of osteocalcin and alkaline phosphatase (ALP). Bone loss was inversely related to calcium and vitamin D intakes and to serum 25-OH vitamin D (25OHD) levels. By multiple regression analyses, only bone density in premenopause, time without estrogens, weight, vitamin D intake, and serum ALP levels remained as independent predictors of present bone mass or bone loss. This study emphasizes the importance of building a good bone mass before menopause, of having adequate vitamin D intake, and of beginning estrogen replacement therapy as soon as possible to minimize bone loss in the first years of menopause.