Obesity is a significant public health threat, with populations of low socioeconomic status (SES) at greatest risk. To reduce and eventually eliminate socioeconomic disparities in obesity and related diseases, it is critical to identify and address factors that contribute to energy imbalance, resulting largely from a combination of poor dietary practices and insufficient physical activity, among low SES populations. Environmental contributions to obesity are of growing interest. However, studies to date have likely underestimated the role the environment plays in health behaviors and body weight status, and related disparities, by focusing solely on neighborhoods where people live (residential neighborhoods), instead of the broader spaces in which individuals routinely travel to engage in activities (activity space). Measuring aspects of activity-space environments could provide new insights into environmental contributions to socioeconomic disparities in obesity and related health behaviors.  However, little is known about the feasibility of the intensive data collection approach required to measure individuals’ activity spaces and concurrently health behaviors. The purpose of this study is to pilot-test seven days of data collection with 75 urban African-American and white adults using (a) portable global positioning system (GPS) units to measure activity space, (b) accelerometers to measure physical activity, and (c) three 24-hour dietary recalls to measure dietary intake. The specific aims are (1) to examine the feasibility of the data collection approach (e.g. adherence rate for each data collection method, technical problems encountered) and (2) to explore relationships between measures of activity-space size and environmental resources/risks (e.g., activity friendliness; physical deterioration; spatial accessibility of parks, supermarkets, fast food restaurants) and (a) individual SES and (b) health behaviors and body weight status (BMI, waist circumference).  This study will be conducted as part of the Healthy Environments Partnership (HEP), a community-based participatory research (CBPR) collaboration in Detroit.  A probability sample of African-American and White adults who participate in HEP’s funded second wave survey (scheduled for Summer 2008) will be invited to take part in this supplemental study. Results of this study will inform a large scale study to examine relationships among individual SES, activity-space and residential neighborhood environmental resources/risks, health behaviors, and body weight status.  In the long-term, results have implications for policies related to land use, zoning and economic development, among others.