The authors investigated the age of onset of the menopause by random selection, using a questionnaire, in 344 women aged 43 to 90 years in relation to smoking. They evaluated 107 non-smokers, 112 passive smokers, and 118 active smokers. The mean age of onset of the menopause in non-smokers was 49.8 +/- 4.1, in passive smokers 49.1 +/- 4.9 and in active smokers 48.1 +/- 4.3 years. Active smokers had their menopause on average by 1.7 years sooner than non-smokers (p less than 0.01). This difference depended on the duration of smoking and increased with the number of smoked cigarettes to as much as 2.4 years in smokers of greater than 20 cigarettes per day and to three years when also the mother of the investigated woman was a smoker (p less than 0.01).