NHIS is an annual, in-person interview survey of the health status and behaviors of the noninstitutionalized U.S. population of all ages. The analysis described in this report used the sample adult component, which is limited to persons aged ≥18 years. One adult per selected household was chosen randomly to participate. Because NHIS oversamples blacks, Hispanics, and Asians, persons in these populations aged ≥65 years have twice the probability of being selected, compared with other adults. For this analysis, NHIS data from 2007, 2008, and 2009 were combined, and annualized prevalence estimates were calculated and stratified by selected characteristics (i.e., sex, age group, race/ethnicity, education level, body mass index (BMI) category,* physical activity level,† and smoking status). Unweighted sample sizes were 23,393 in 2007; 21,781 in 2008; and 27,731 in 2009. Response rates for the sample adult component were 67.8% in 2007, 62.6% in 2008, and 65.4% in 2009.‡ Respondents were defined as having doctor-diagnosed arthritis if they answered “yes” to “Have you ever been told by a doctor or other health professional that you have some form of arthritis, rheumatoid arthritis, gout, lupus, or fibromyalgia?” Those who responded “yes” to having doctor-diagnosed arthritis were asked “Are you limited in any way in any of your usual activities because of arthritis or joint symptoms?” Those responding “yes” to both questions were categorized as having AAAL.