From 1971-1991 the Occupational Health Service of Los Angeles Country measured physical fitness and other CHD risk factors (including physical activity, anthropometric measures, blood pressure, smoking, family history of CHD, and levels of total cholesterol, uric acid, and glucose) in Los Angeles County firefighters at application and routine intervals (approximately every three years). The entire cohort of 3403 firefighters is now followed for mortality up to 1996.