Osteoporosis is a significant health problem and contributor to disability and premature mortality among older men. Incidence rates for hip fracture have stabilized in women, but continue to increase in men. A major risk factor for hip fracture is bone mineral density level. The determinants of bone mineral density (BMD) are well defined in women, but not in men. The primary goal of the current research was to increase our understanding of the determinants of BMD of the proximal femur in a large community-based sample of older male volunteers. Eligibility requirements included age of 50 years or older, ambulatory, and not having undergone a bilateral hip replacement. Five hundred twenty-three men, mean age 66.6 years, met all eligibility requirements and participated in the Study of Osteoporotic Risk in Men or STORM. Information on demographics, medical history, anthropometry, leisure-time and occupational physical activity, muscular strength, cigarette smoking, alcohol consumption, dietary calcium intake, and medication use (thiazide diuretics and glucocorticoids) were obtained by questionnaire, interview, and examination. BMD of the proximal femur (femoral neck, greater trochanter, and Ward's triangle) was measured by dual-energy X-ray absorptiometry using the Hologic QDR-1000 and QDR-2000. The cross-sectional determinants of BMD included age, blond hair color, current body weight, thiazide diuretic use, historical physical activity, and quadriceps strength. Several variables commonly thought to be determinants of BMD were not related to BMD in this population of older men, including current cigarette smoking, alcohol consumption, current leisure-time physical activity, dietary calcium intake, vitamin D use, and caffeine intake. However, failure to find associations among BMD and some of the potential determinants may be due to lack of statistical power. Identification of the determinants of BMD could lead to the development of interventions aimed at maximizing BMD in men and could potentially decrease the risk of hip fractures.