OBJECTIVES: Physical function limitation and muscle wasting are commonly associated with many chronic conditions and the aging process. The National Health and Nutrition Examination Survey (NHANES) 2001-2002 include a physical function limitation questionnaire, as well as examinations measuring muscle mass and muscle strength. The factor structure of the physical function limitation questionnaire, however, is unknown. The aim of this study was to evaluate the factor structure of this questionnaire, and to examine the relationship between physical function and muscle measurements in the elderly in the United States. METHODS: Data from NHANES 2001-2002 participants aged 60-80 years (n=1394) was used for this study.  First, a maximum likelihood based exploratory factor analysis (EFA) with Geomin rotation (an oblique rotation) of the nineteen physical function limitation items was implemented. The relationship among the identified questionnaire domains, muscle strength (as measured by isokinetic strength of the knee extensors), and muscle mass (as measured by appendicular skeleton muscle mass index) were examined using partial correlation coefficient (PCC) adjusted for age, gender, and percentage of body fat. RESULTS: The EFA produced a 3-factor solution for items measuring gross motor function, fine motor function, and social and entertainment function. The three domains were moderately correlated with each other (PCC=0.5 to 0.6, p<0.001). Muscle strength was weakly related with limitations in gross motor function (PCC=-0.20, P<0.001), and social and entertainment function (PCC=-0.13, P<0.001); but not significantly related with limitation in fine motor function (PCC=-0.06, p=0.09). CONCLUSIONS: These findings suggest that in a sample of US elderly aged 60-80 years the NHANES physical function limitation questionnaire has three domains, of which the gross motor function domain and social and entertainment function domain are weakly related with muscle strength.