Does a new supermarket improve dietary behaviors of low-income African Americans? Obesity poses a serious threat to the health of our nation. Two thirds of adults in the United States are either overweight or obese, and low-income and racial/ethnic minorities are disproportionately affected. Poor dietary quality and patterns are key risk factors for obesity, and both diet and obesity are established risk factors for cancer and other chronic diseases. Increasing evidence suggests that modifying the food environment to support healthy eating may have a sustainable population impact on diet and obesity. Yet, environmental approaches are understudied. In 2010, an 8.5 million dollar full-service grocery store, financed with public and private funds, will change the food retail landscape of the Hill District, a collection of contiguous neighborhoods of Pittsburgh, Pennsylvania. This joint public-private endeavor provides a unique and critically timed opportunity to examine how change in the availability of healthy foods affects food purchasing and dietary intake of residents in a US community. This full-service grocery store will be the first in nearly 30 years for this low-income, predominantly African-American community. The proposed study will capitalize on this natural experiment. Our specific aims are (1) to describe the availability, price, and shelf-space of healthy and less healthy options within food retail venues before and after the introduction of a full-service grocery store; (2) to determine the impact of the introduction of a full-service grocery store on food purchasing behaviors and dietary intake; and (3) to determine the extent to which these associations are modified by access factors (e.g., means of transportation and degree of spatial proximity to the grocery store) and socio-cultural factors (e.g., attitudes toward eating a healthy diet, perceived barriers to eating a healthy diet, and social support for healthy eating). We propose to use a matched quasi-experimental design involving one pre- and two post-intervention assessments of 1,000 households in the Hill District and 650 households in matched comparison neighborhood. Using door-to-door surveys, we will collect information on participants' household food purchasing and individual dietary intake. We will also conduct pre- and post- assessments of the food environment in the intervention and comparison neighborhoods. The food environment assessments will document the number and type of food purchasing venues and assess availability, quality, and price of healthy foods in these venues. Collectively, these data will allow us to examine how opening a full-service grocery store in a low-income, predominantly African American neighborhood, affects peoples' diet and food purchasing behaviors in both the short and long term. Our study will fill significant gaps in the literature on environmental determinants of diet and obesity and will help address key policy questions about the effects of the physical environment on these outcomes.