We reviewed prominent audit tools used to assess the physical environment of parks and their potential to promote physical activity. To accomplish this, we manually searched the Active Living Research website (http://www.activelivingresearch.com) for published observational audit tools that evaluate the physical environment of parks, and we reviewed park audit tools used in studies included in a systematic review of observational park-based physical activity studies. We identified 5 observational audit tools for review: Bedimo-Rung Assessment Tool-Direct Observation (BRAT-DO), Community Park Audit Tool (CPAT), Environmental Assessment of Public Recreation Spaces (EAPRS) tool, Physical Activity Resource Assessment (PARA), and Quality of Public Open Space Tool (POST). All 5 tools have established inter-rater reliability estimates ranging from moderate to good. However, BRAT-DO is the only tool with published validity. We found substantial heterogeneity among the 5 in length, format, intended users, and specific items assessed. Researchers, practitioners, or community coalition members should review the goal of their specific project and match their goal with the most appropriate tool and the people who will be using it.