CONCLUSIONS Risk factors for hip fracture were studied in 7,495 randomly selected men during 30 years; 451 men had a hip fracture. High degree of leisure-time, but not work-related, physical activity, high occupational class, and high body mass index (BMI) protected against hip fracture. Smoking, tall stature, interim stroke, and dementia increased the risk. OBJECTIVE The purpose was to prospectively study risk factors for hip fracture in men. METHODS We studied midlife determinants of future hip fractures in 7,495 randomly selected men aged 46-56 years in Gothenburg, Sweden. The subjects were investigated in 1970-1973 and followed for over 30 years. Questionnaires were used regarding lifestyle factors, psychological stress, occupational class, and previous myocardial infarction, stroke, and diabetes mellitus. Alcohol problems were assessed with the aid of registers. Using the Swedish hospital discharge register, data were collected on intercurrent stroke and dementia diagnoses and on first hip fractures (X-ray-verified). RESULTS Four hundred fifty-one men (6%) had a hip fracture. Age, tall stature, low occupational class, tobacco smoking, alcoholic intemperance, and interim stroke or dementia were independently associated with the risk of hip fracture. There were inverse associations with leisure-time physical activity, BMI, and coffee consumption. The gradient of risk for one standard deviation of multivariable risk decreased with time since measurement yet was a good alternative to dual energy X-ray absorptiometry measurements. CONCLUSIONS High degree of leisure-time physical activity, high occupational class, and high BMI protected against hip fracture. However, work-related physical activity was not protective. Smoking, tall stature, and interim stroke or dementia increased the risk.