In order to clarify the effect of smoking on androgen status in the early post-menopause we examined 267 women aged 45-54 years, of whom 146 (55%) were smokers. The cigarette smokers had a significantly higher serum concentration of androstenedione (P less than 0.001) and a raised serum concentration of luteinizing hormone (P = 0.06) in comparison with the non-smokers. The number of cigarettes consumed was apparently immaterial. The concentrations of oestrone, oestradiol and follicle-stimulating hormone were similar in the two groups. This study lends support to the hypothesis that the observed decreased risk of endometrial and breast cancer associated with cigarette smoking may be mediated by androgenic protection.