Background: Inter-rater reliability is an important element of environmental audit tools. This paper presents results of reliability tests of the Irvine-Minnesota Inventory, an extensive audit tool aimed at measuring a broad range of built environment features that may be linked to active living. Methods: Inter-rater reliability was measured by percentage agreement between observers. Reliability was tested on a broad range of sites in both California and Minnesota. Results: For the variables that remained in the inventory, in tests conducted at the University of California-Irvine, 76.8% of the variables had >80% agreement among the three raters. In tests conducted at the University of Minnesota, 99.2% of the variables had >80% agreement among the two raters. Conclusions: Reliability was high for most items. The inventory was modified to eliminate items with low reliability. Differences in the use of the inventory and the goals of the research led to generally higher reliability in Minnesota. Those differences, limitations, and directions for future research are discussed.