The present study prospectively examined the age at menopause of 92 women with Down's syndrome (DS) and the influence of hypothyroidism on the age of menopause. Three methods were used to determine the distribution and median age at onset of menopause: (1) Kaplan-Meier life tables; (2) Cox proportional hazards modelling; and (3) maximum likelihood logistic regression. All three methods provided distributions and similar estimates of the median age at menopause, which was approximately 46 years. The presence of hypothyroidism did not influence age at menopause. The earlier-than-expected age at onset of menopause suggests that women with DS are at an increased risk for post-menopausal health disorders.