We used the AAMR's Adaptive Behavior Scale to ascertain current menstrual status in a population-based sample of 157 women with Down's syndrome (DS) and 187 women with other intellectual disability, all 40 years of age or older. The age-adjusted likelihood of menopause was twice as high in women with DS syndrome as in women with other intellectual disability (OR = 2.3; 95% CI = 1.1-4.9). Treated thyroid conditions did not influence menstrual status and did not modify the relationship between DS and menstrual status. These findings support the hypothesis that women with DS experience menopause at an earlier age and that this may be associated with accelerated aging.