We investigated whether age at menopause is associated with subsequent mortality from colorectal cancer along with the possible modification of this association by body mass index. Our data are from the Diagnostisch Onderzoek Mammacarcinoom cohort of 10,671 postmenopausal women in the Netherlands, enrolled between 1974 and 1977, with a median follow-up of 18 years. During this follow-up, 95 women died of colorectal cancer. Women 49 years of age or older at menopause showed a lower risk of colorectal cancer mortality compared with women younger than 49 at menopause. This protective effect, however, was found only among nonoverweight women (< or =24 kg/m2), for whom the hazard ratio was 0.46 (95% confidence interval = 0.21-1.03). In larger women, the hazard ratio was 1.17 (95% confidence interval = 0.68-2.00).