To determine how physical characteristics of trails may influence use, reliable and valid audit tools are needed. The Path Environment Audit Tool (PEAT) was developed with design, amenity, and aesthetics/maintenance items. Two observers independently audited 185 trail segments at 6 Massachusetts facilities. GPS-derived items were used as a "gold standard." Kappa (k) statistics, observed agreement and ICCs were calculated to assess inter-observer reliability and validity. Fifteen of 16 primary amenity items had k-values > 0.49 ("moderate") and all had observed agreement > 81%. Seven binary design items had k-values ranging from 0.19 to 0.69 and three of 5 ordinal items had ICCs > 0.52. Only two aesthetics/maintenance items (n=7) had moderate ICCs. Observed agreement between PEAT and GPS items was > 0.77; k-values were > 0.57 for 7 out of 10 comparisons. PEAT has acceptable inter-observer reliability and validity for most of its primary items and appears ready for use by researchers and practitioners. (Source: Active Living Research)