Although early natural menopause has been postulated to increase stroke risk, studies have not produced convincing results. We examined the associations between stroke risks and age at natural menopause or time since natural menopause. 5,731 naturally postmenopausal women more than 65 yr of age were followed from 1993 to 1998. Information on age at menopause and risk factors were obtained using mailed questionnaires. 186 cases of stroke occurred over a total 27,936 person-years. After adjusting for age, hypertension, and physical activity, age at menopause was not found to be significantly associated with stroke or cerebral infarction. However, adjusted relative risks (aRRs) showed a significant increasing tendency of hemorrhagic stroke versus age at menopause (aRRs, 0.66, 0.48, 1.00 and 2.33 for the following age groups at menopause; 40-44, 45-49, 50-54 [reference group], and >= 55 yr). Time since menopause (11-20, 21-30, and >= 31 yr) was not found to be significantly associated with cerebral infarction, or hemorrhagic stroke. Late menopause (menopause age >= 55 yr) showed a tendency of a lower risk of cerebral infarction (aRR, 0.79) and a higher risk of hemorrhagic stroke (aRR, 2.33). Further study is warranted to determine stroke risk in women during the decade following menopause.