The 1996 Surgeon General's Report on Physical Activity and Health emphasized the health-related benefits of moderate-intensity physical activities (PA), such as heavy yard work, brisk walking, and housework. Prior to this, vigorous intensity PA (e.g., running, aerobic sports) was recommended for cardiovascular health. Given the public health focus on lifestyle activities, traditional surveillance systems with an emphasis on vigorous intensity sports are not able to determine how many Americans are achieving a level of PA to ensure health benefits. PURPOSE To determine the prevalence and epidemiology of health-related PA levels in U.S adults using a new instrument designed to capture a broad range of activities. METHODS Data were obtained in 2001 from a population-based randomdigit-dialed telephone survey administered to adults. Survey questions assessed PA while at work and during leisure time. RESULTS The study population included 83,684 men and 121,456 women. About 45% of adults were active at recommended levels (men 48%; women 43%) and only 16% reported no leisure-time PA. As expected, the prevalence of recommended levels of PA decreased as age increased and the prevalence of recommended activity was higher among whites compared to Blacks or Hispanics. Differences were noted by educational level with recommended levels of PA increasing as educational level increased. At work, 9% reported heavy activity, 14% reported mostly standing and walking, 39% reported mostly sitting and 38% were unemployed. Among men reporting heavy labor, over 50% were active at the recommended level in their non-working hours. CONCLUSION Broadening the definition of PA to include moderate-intensity activities increased the prevalence of recommended activity to 45%, suggesting that over half the population is still at risk for poor health outcomes due to physical inactivity.