Early age at menopause is a major determinant of the lifetime risks of cardiovascular diseases, osteoporosis, and less markedly of breast and genital tract cancers. Thus a definition of the determinants of age at menopause has potential speculative interest as a means of identifying women and quantifying the risk for these conditions. The authors analysed the mean age at menopause and its determinants in about 31,000 women attending menopause clinics in Italy. The authors considered 31,834 women aged 55 years or more and in spontaneous menopause who had entered the study up until March 2003. Spontaneous menopause was defined as natural cessation of menses for 12 or more months. The mean age at spontaneous menopause was 51.2. The age at menopause did not markedly changed with cohort of birth. Higher education was associated with lower age at menopause (51.1 in women with low education vs 51.3 for women with high school or university degree). A higher BMI was associated with later age at menopause. Smokers reported a lower age at menopause (51.2 in nonsmokers vs 51.1 in smokers). A later age at menarche was associated with a later age at menopause. Likewise, lifelong irregular menstrual cycles and higher parity were related with later age at menopause. No association emerged between ever oral contraceptive use and age at menopause. Low educational level, lower BMI, smoking, early menarche, nulliparity, and regular cycles are independently associated with lower age at natural menopause in a large sample of women attending menopause clinics in Italy.