This paper describes bone mineral levels in the proximal femur of US adults based on a nationally representative sample of 7116 men and women aged 20 years and older. The data were collected in phase 1 of the third National Health and Nutrition Examination Survey (NHANES III, 1988-1991) using dual-energy X-ray absorptiometry, and included bone mineral density (BMD), bone mineral content (BMC) and area of bone scanned in five selected regions of interest (ROI) in the proximal femur: femur neck, trochanter, intertrochanter, Ward's triangle and total. These variables are provided separately by age and sex for non-HIspanic whites (NHW), non-Hispanic blacks (NHB) and Mexican Americans (MA). BMD and BMC in the five ROI tended to decline with age, whereas area did not. BMD and BMC were highest in NHB, intermediate in MA and lowest in NHW, but areas were highest in NHW, intermediate in NHB and lowest in MA. Men had greater BMD, BMC and area than women in all three race/ethnic groups. Differences by age, sex or race/ethnicity tended to be the largest in Ward's triangle, followed by the femur neck; patterns in the trochanter, intertrochanter and total ROI were reasonably similar to each other. This report provides extensive data on femur bone mineral levels of adults from one of the largest samples available to date and should be valuable as reference data for other studies which examine this skeletal site in adults.