Here at the start of the 21st century our understanding of which factors promote health and which damage health has grown considerably. The diseases of the 21st century will be “chronic” diseases, those that steal vitality and productivity, and consume time and money. These diseases-heart disease, diabetes, obesity, asthma, and depression- are diseases that can be moderated by how we design and build our human environment. It is now accepted that, in addition to direct hazards from infectious diseases and environmental toxins, human behaviors play a critical role in determining human health. As we begin to include consideration of these factors into our health-related decision-making, we must additionally guard against using too narrow a definition of the environment. Every person has a stake in environmental public health, and as environments deteriorate, so does the physical and mental health of the people who live in them. There is a connection, for example, between the fact that the urban sprawl we live with daily makes no room for sidewalks or bike paths and the fact that we are an overweight, heart disease-ridden society. Obesity can increase the risk of (adult-onset) type 2 diabetes by as much as 34 fold, and diabetes is a major risk factor for amputations, blindness, kidney failure, and heart disease. The most effective weight loss strategies are those that include an increase in overall physical activity. In a recent type 2 diabetes trial, weight loss and physical activity were more effective in controlling the disease than medication. In addition, for treatment of relatively mild cases of anxiety and depression, physical activity is as effective as the most commonly prescribed medications. It is dishonest to tell our citizens to walk, jog, or bicycle when there is no safe or welcoming place to pursue these “life-saving” activities. Respiratory disease, especially asthma, is increasing yearly in the U.S. population. Bad air makes lung diseases, especially asthma, worse. The more hours in automobiles, driving over impervious highways that generate massive tree-removal, clearly degrade air quality. When the Atlanta Olympic Games in 1996 brought about a reduction in auto use by 22.5%, asthma admissions to ERs and hospitals also decreased by 41.6%. Less driving, better public transport, well designed landscape and residential density will improve air quality more than will additional roadways. In order to address these critical health problems we must seize opportunities to form coalitions between doctors, nurses, and public health professionals and others such as architects, builders, planners and transportation officials, so that we are all “at the table” when environmental decisions are made. Such decisions include whether to install sidewalks in the next subdivision. It means thinking about what constitutes safe and affordable housing, safe neighborhoods, providing green space for people to enjoy where they live and work, and rethinking how we travel from one place to another. Land-use decisions are just as much public health decisions as are decisions about food preparation. What, for example, are the implications for children with asthma of building yet another expressway? We must also question whether a fatality involving a pedestrian isn’t actually the result of poor urban planning, thoughtless land use, or inferior urban design rather than “simply” a motor vehicle crash. We must be alert to the health benefits, including less stress, lower blood pressure, and overall improved physical and mental health, that can result when people live and work in accessible, safe, well-designed, thoughtful structures and landscapes. We must measure the impact of environmental decisions on real people, and we must begin, in earnest, to frame those decisions in light of the well being of children, not only in this country but across the globe.