The article reviews the state of the science in measuring the built environment for physical activity, focusing on three categories of measures: perceived measures, observational (audit) measures, and GIS-derived measures. Perceived measures, obtained through telephone interviews or self-administered questionnaires, assess individuals' perceptions of their environment. Observational measures, or audits, involve systematic observations to quantify environmental attributes. GIS-derived measures use existing data sets and are often analyzed with GIS. The review highlights the variability in operationalization of common GIS measures and the need for further development and evaluation of these measures. It also discusses the challenges and future directions in improving the technical quality, relevance to various population groups, and utility for science and public health. The article emphasizes the importance of standardized definitions, validated measures, and the inclusion of socio-political variables to enhance the understanding of the built environment's impact on physical activity.The article reviews the state of the science in measuring the built environment for physical activity, focusing on three categories of measures: perceived measures, observational (audit) measures, and GIS-derived measures. Perceived measures, obtained through telephone interviews or self-administered questionnaires, assess individuals' perceptions of their environment. Observational measures, or audits, involve systematic observations to quantify environmental attributes. GIS-derived measures use existing data sets and are often analyzed with GIS. The review highlights the variability in operationalization of common GIS measures and the need for further development and evaluation of these measures. It also discusses the challenges and future directions in improving the technical quality, relevance to various population groups, and utility for science and public health. The article emphasizes the importance of standardized definitions, validated measures, and the inclusion of socio-political variables to enhance the understanding of the built environment's impact on physical activity.