With the aging of the world's population, the social and economic implications of osteoporotic fractures are at epidemic proportions. This study was performed to test the hypothesis that a proximal humeral fracture is an independent risk factor for a subsequent hip fracture and that the risk of the subsequent hip fracture is highest within the first five years after the humeral fracture. Methods: A cohort of8049 olderwhite women with no history of a hip or humeral fracture who were enrolled in the Study of Osteoporotic Fractures was followed for a mean of 9.8 years. The risk of hip fracture after an incident humeral fracture was estimated with use of age-adjusted Cox proportional hazards regression analysis with time-varying variables; women without a humeral fracture were the reference group. Cox regression analysis was used to evaluate the timing between the proximal humeral and subsequent hip fracture. Risk factors were determined on the basis of a review of the current literature, and we chose the variables that were most predictive and easily ascertained in a clinical setting. Results: Three hundred and twenty-one women sustained a proximal humeral fracture, and forty-four of them sustained a subsequent hipfracture. Afteradjustment forage and bone mineral density, the hazard ratiofor hipfracture for subjects with a roximal humeral fracture relative to those without a proximal humeral fracture was 1.83 (95% confidence interval = 1.32 o 2.53). After multivariate adjustment, this risk appeared attenuated but was still significant (hazard ratio = 1.57; 95% onfidence interval = 1.12 to 2.19). The risk of a subsequent hipfracture aftera proximal humeral fracture was highest within ne year after the proximal humeral fracture, with a hazard ratio of 5.68 (95% confidence interval = 3.70 to 8.73) his association between humeral and hip fracture was not significant after the first year, with hazard ratios of 0.87 (95% onfidence interval = 0.48 to 1.59) between one and five years after the humeral fracture and 0.58 (95% confidence interval = 0.22 to 1.56) after five years. onclusions: In this cohort of older white women, a proximal humeral fracture independently increased the risk of a ubsequent hip fracture more than five times in the first year after the humeral fracture but was not associated with a ignificant increase in the hip fracture risk in subsequent years. Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.