BACKGROUND Physical activity has numerous health benefits, including improving weight management. The 2008 Physical Activity Guidelines for Americans recommend ≥150 minutes/week of moderate-intensity aerobic physical activity (e.g., brisk walking) for substantial health benefits. Walking is the most commonly reported physical activity by U.S. adults. METHODS CDC used data from the 2005 and 2010 National Health Interview Surveys to assess changes in prevalence of walking (defined as walking for transportation or leisure in at least one bout of 10 minutes or more in the preceding 7 days) by sex, age group, race/ethnicity, education, body mass index category, walking assistance status, region, and physician-diagnosed chronic disease. CDC also assessed the association between walking and meeting the aerobic physical activity guideline. RESULTS Overall, walking prevalence increased significantly from 55.7% in 2005 to 62.0% in 2010. Significantly higher walking prevalence was observed in most demographic and health characteristic categories examined. In 2010, the adjusted odds ratio of meeting the aerobic physical activity guideline among walkers, compared with non-walkers, was 2.95 (95% confidence interval = 2.73-3.19). CONCLUSIONS AND IMPLICATIONS FOR PUBLIC HEALTH PRACTICE: To sustain increases in the prevalence of walking, communities can implement evidence-based strategies such as creating or enhancing access to places for physical activity, or using design and land use policies and practices that emphasize mixed-use communities and pedestrian-friendly streets. The impact of these strategies on both walking and physical activity should be monitored systematically at the national, state, and local levels. Public health efforts to promote walking as a way to meet physical activity guidelines can help improve the health of U.S. residents.