['Although changes in body weight with aging are common, little is known about the effects of weight change on health in old age.', 'To study the effects of weight loss and weight gain from age 50 years to old age on the risk of hip fracture among postmenopausal white women aged 67 years and older and to determine if the level of weight at age 50 years modifies this risk.', 'The association between weight change and the risk of hip fracture was studied in 3683 community-dwelling white women aged 67 years and older from three sites of the Established Populations for Epidemiologic Studies of the Elderly.', 'Extreme weight loss (10% or more) beginning at age 50 years was associated in a proportional hazards model with increased risk of hip fracture (relative risk [RR], 2.9; 95% confidence interval [CI], 2.0-4.1). This risk was greatest among women in the lowest (RR, 2.3; CI, 1.1-4.8) and middle (RR, 2.8; CI, 1.5-5.3) tertiles of body mass index at age 50 years. Among the thinnest women, even more modest weight loss (5% to < 10%) was associated with increased risk of hip fracture (RR, 2.3; CI, 1.0-5.2). Weight gain of 10% or more beginning at age 50 years provided borderline protection against the risk of hip fracture (RR, 0.7; CI, 0.4-1.0). The RRs for weight gain of 10% or more were protective only among women in the middle and high tertiles of body mass index at age 50 years and were not significant (middle tertile RR, 0.8; CI, 0.3-1.8; high tertile RR, 0.6; CI, 0.2-1.9).'] Is weight change between age 50 years and old age associated with risk of hip fracture in white women aged 67 years and older?