Behavioral medicine scientists are well aware of the negative health consequences of an inactive lifestyle and obesity. The numbers are alarming: at least 300,000 premature deaths a year, significant increased risk for chronic diseases such as cardiovascular disease (CVD) and type 2 diabetes, consequent reduced quality and quantity of life, and more than $90 billion a year in direct U.S. health care costs (1). The percentage of obese U.S. adults has increased 74% between 1991 and 2001 (2), and the estimated current prevalence of obesity may be as high as 31% of adults (3). An estimated 75% of U.S. adults do not meet the recommended 30 min of moderate leisure-time activity on most days of the week, and about 33% are completely sedentary (4). In the past few years, the scientific literature and popular press have brought to our attention that the situation is equally bad or perhaps worse for adolescents and children (5,6). An emerging paradigm for addressing this health crisis is to examine the problem from an ecological perspective, not only to consider the intrapersonal and interpersonal factors that determine sedentary lifestyles but also to examine the impact of the physical environment and the broader concept of “Active Living” (7–9). According to this perspective, in the last half-century we have engineered physical activity out of our lives. Our communities are built to facilitate driving for transportation rather than walking or bicycling, labor-saving devices allow us to expend little energy on household tasks, and sedentary leisure activities seem to be attractive alternatives to more physically active options. As a result, walking, which is arguably the most basic of human behaviors for transportation and leisure, has been slowly eliminated by our own design. Studies show that the more moderate activity of walking can provide nearly all of the physical and mental health benefits of more vigorous forms of activity such as reduced risk for chronic diseases (e.g,. CVD, stroke, type 2 diabetes, anxiety, and depression) and decreased risk of all-cause mortality (10). Walking is the recommended activity prescription in a number of studies (11–14) and has the advantages of not requiring any special equipment or skills and being cost free. In addition, it can be done individually or in groups. This issue of Annals of Behavioral Medicine includes two articles that focus on walking. Fisher and Fuzhong report on a randomized trial of 56 neighborhoods to evaluate a 6-month walking group program for older adults (15). They found significant improvements on measures of physical and mental functioning and life satisfaction and in the amount of walking activity for intervention neighborhoods compared to control neighborhoods. This study demonstrates that a low-cost community-level intervention can positively impact not only activity levels but also perceived quality of life for neighborhoods. The community walking program did not require any special facilities or equipment and worked within each neighborhood’s existing environment. The study also demonstrates the feasibility of implementing a simple community program that can increase social support and enhance perceptions of the existing environment (e.g., reducing barriers, such as concerns about safety, and providing convenient walking routes). This study is a superb example of applying an ecological framework and revealing multiple program benefits to the community. Also in this issue, Tudor-Locke et al. tackle the basic issue of measuring walking behavior (16). Tudor-Locke and her colleagues previously published a number of studies on the use of pedometers for measuring walking activity (17–19). These inexpensive and unobtrusive devices are a great tool for providing feedback to individuals about the amount of steps they take. Step counts from pedometers have the potential to be an objective outcome measure and a motivating feedback mechanism for activity interventions. However, the field is still grappling with basic issues such as pedometer accuracy, step norms for different groups, factors that influence the variability of steps, and translation of health recommendations into steps-per-day guidelines. Tudor-Locke et al.’s article presents observational research of a full year of continuous self-monitoring using pedometers to determine the sources of natural variability of walking in an effort to better understand how to accurately measure steps with a pedometer. The findings revealed seasonal and weekly natural fluctuations in steps per day as well as individuals’ misperceptions about when they engaged in more or less activity. These misperceptions further emphasize the problems of relying on self-reported recalls of physical activity that are often used in epidemiological and experimental studies of physical activity (20,21) and the need for the use of objective measures of activity, especially when the emphasis is on moderate lifestyle activities.