OBJECTIVE Numerous studies have been focused on the detection of factors which can act on the age of menopause. Little is known about the factors related to the occurrence of an early menopause. Some factors such as occupational work factors and generational effects have not been taken into account as yet. METHODS We examined the risk factors of early natural menopause (before age 45) in a large random sample of gainfully employed French women born in the years 1938 (n = 1743) and 1943 (n = 1959). The subjects were selected from files of an occupational physician. A woman was considered to be post-menopausal when at least 12 consecutive months had passed without menstruation at the time of the survey. Subjects were questioned and examined during their annual visit by the occupational physician. Occupational history, working conditions, living conditions, smoking habits and reproductive history were explored. RESULTS The prevalence of early natural menopause, before age 45, was higher in the generation of 1938 (5.3%) than in that of 1943 (3.3%) with P < 0.01. After multivariate regressions, significant relationships existed statistically between the occurrence of early natural menopause and marital status, educational level, age at first childbirth and breast-feeding of children. CONCLUSIONS Our results show important generation effects. There was no evidence of a significant relationship between early natural menopause at 45 years of age and factors relative to heavy physical work conditions.