BACKGROUND The Americans With Disabilities Act defines disability on the basis of physical or mental impairments or external perceptions of impairment. OBJECTIVE The objective of this study was to examine perceptions of disability among people with lower-extremity mobility difficulties. METHODS This study used a cross-sectional, nationally representative survey, the 1994 to 1995 National Health Interview Survey-Disability (NHIS-D) supplement. Using SAS-callable SUDAAN for all analyses, we produced national population estimates. METHODS This study included 142,572 noninstitutionalized, civilian residents of the United States who were > or =18 years of age, with 80,423 self-respondents and 49,883 proxy respondents. METHODS We created a 4-level mobility variable using NHIS-D questions about the ability to walk, climb stairs, stand and the use of mobility aids. We examined associations between mobility and answers to 2 questions about self- and external perceptions of disability. RESULTS The results showed that 3.1% (estimated 5.82 million persons) reported major mobility difficulties, including 3.7% of self-respondents and 2.7% of those with proxy respondents. Among persons with major mobility problems, 70.8% perceived themselves as disabled, whereas 64.8% thought other people see them as disabled. Also, 80.5% of manual wheelchair users saw themselves as disabled. Proxies were somewhat more likely to perceive disability than self-respondents, although differences were not generally statistically significant. In multivariable regressions, mobility level was the strongest predictor of self-perceived disability, followed by general health status. CONCLUSIONS Mobility problems increase the likelihood that people will see themselves as disabled, but these perceptions are not universal. Although the schematic of wheelchair users has become an international symbol of disability, many people with serious mobility problems do not view themselves as disabled.