To clarify the relationship between age, menopause, and nonalcoholic fatty liver disease (NAFLD) in women. We conducted a follow-up study on nonalcoholic fatty liver disease by using abdominal ultrasonography, and investigated the relationship of age and menopause with the development of NAFLD in women. We followed 1829 women and 2572 men (response rate, 86%) selected in 2001 to represent the non-institutionalized adult population of Gifu, Japan. Data collected included self-reported medical history, lifestyle factors, and menopausal status. The postmenopausal state was defined as beginning 1 year after the cessation of menses. We diagnosed NAFLD with the aid of abdominal ultrasonography by using diagnostic criteria described previously. The prevalence of NAFLD in women increases with age, but does not alter with age in men. Furthermore, the prevalence of NAFLD in premenopausal women (6%) was lower than that in men (24%) and in postmenopausal women (15%). The associations of the postmenopausal state and hormone replacement therapy with NAFLD were statistically significant in a univariate logistic regression model. At the follow-up examination, 67 women (5%) were newly diagnosed with NAFLD. The incidence of NAFLD was 3.5% (28/802) in premenopausal women, 7.5% (4/53) in menopausal women, 6.1% (24/392) in postmenopausal women, and 5.3% (11/206) in women receiving hormone replacement therapy. The weight gain in premenopausal women was equal to that in postmenopausal women. Metabolic syndrome and weight gain were independent risk factors for NAFLD in pre- and postmenopausal women, but age was an independent risk factor in premenopausal women only. Aging is a risk factor for NAFLD in premenopausal women, independent of weight gain or influence of metabolic syndrome.