This article presents updated data on bone mineral levels in the proximal femur of US adults based on the third National Health and Nutrition Examination Survey (NHANES III), which covered 1988–1994. The data were collected from 14,646 men and women aged 20 years and older using dual-energy X-ray absorptiometry (DXA). The study measured bone mineral density (BMD), bone mineral content (BMC), and the area of bone scanned in four regions of interest (ROI) in the proximal femur: femur neck, trochanter, intertrochanter, and total. These variables are provided separately by age and sex for non-Hispanic whites (NHW), non-Hispanic blacks (NHB), and Mexican Americans (MA). NHW in the southern United States had slightly lower BMD levels than NHW in other regions, but these differences were not large enough to prevent data pooling. The updated data provide valuable reference data on femur bone mineral levels for noninstitutionalized adults. The updated data on BMD for the total femur ROI of NHW have been selected as the reference database for femur standardization efforts by the International Committee on Standards in Bone Measurements. The study also examined potential geographic variation in BMD among US adults, comparing BMD levels in four broad regions as defined by the Bureau of the Census. The data were collected using a highly stratified, multistage probability design to select a representative sample of the civilian, noninstitutionalized US population. The study used three densitometers to obtain measurements and implemented a rigorous quality control program to ensure data quality. All men and nonpregnant women aged 20 years and older who received the physical examination were eligible for bone densitometry unless they had fractured both hips previously. The left hip was scanned unless there was a history of previous fracture or surgery. Individuals with an acceptable scan of the right hip were included in the analyses, since their inclusion did not alter estimates.This article presents updated data on bone mineral levels in the proximal femur of US adults based on the third National Health and Nutrition Examination Survey (NHANES III), which covered 1988–1994. The data were collected from 14,646 men and women aged 20 years and older using dual-energy X-ray absorptiometry (DXA). The study measured bone mineral density (BMD), bone mineral content (BMC), and the area of bone scanned in four regions of interest (ROI) in the proximal femur: femur neck, trochanter, intertrochanter, and total. These variables are provided separately by age and sex for non-Hispanic whites (NHW), non-Hispanic blacks (NHB), and Mexican Americans (MA). NHW in the southern United States had slightly lower BMD levels than NHW in other regions, but these differences were not large enough to prevent data pooling. The updated data provide valuable reference data on femur bone mineral levels for noninstitutionalized adults. The updated data on BMD for the total femur ROI of NHW have been selected as the reference database for femur standardization efforts by the International Committee on Standards in Bone Measurements. The study also examined potential geographic variation in BMD among US adults, comparing BMD levels in four broad regions as defined by the Bureau of the Census. The data were collected using a highly stratified, multistage probability design to select a representative sample of the civilian, noninstitutionalized US population. The study used three densitometers to obtain measurements and implemented a rigorous quality control program to ensure data quality. All men and nonpregnant women aged 20 years and older who received the physical examination were eligible for bone densitometry unless they had fractured both hips previously. The left hip was scanned unless there was a history of previous fracture or surgery. Individuals with an acceptable scan of the right hip were included in the analyses, since their inclusion did not alter estimates.