PURPOSE: To test the reliability of the Active Neighborhood Checklist (the Checklist), a user-friendly audit tool for assessing neighborhood environmental supports for physical activity. METHODS: Sixty-four street segments in St. Louis and southeastern Missouri were selected among diverse areas that varied with respect to socioeconomic levels, urbanization, and land use. Fifteen public health researchers and seven community stakeholders conducted audits in April 2005 following a two-hour training session. Interrater reliability was measured for the items in each section of the Checklist (land use characteristics, sidewalks, shoulders and bike lanes, street characteristics, and quality of the environment for a pedestrian) using observed agreement and the kappa statistic. RESULTS: The mean observed agreement for 57 evaluated items was 0.87 (range, 0.61-1.00). The mean kappa statistic was 0.68 (range, 0.21-1.00). DISCUSSION: With minimal training of the auditors, the Checklist demonstrated strong reliability. Future studies are needed to provide information about its usability for various stakeholders and across different settings.