The Scottish Walkability Assessment Tool (SWAT) was designed to objectively record aspects of the physical environment believed to be related to walking in urban Scotland. Reliability was assessed by three pairs of trained raters auditing 30 street segments on two occasions. Eighteen items were reliably audited and displayed adequate environmental variability, 25 items proved unreliable, and 69 items lacked adequate environmental variability. The large number of items that lacked environmental variability indicates a relatively uniform environment in terms of characteristics, which the literature indicates might be used to differentiate walkability; however, the 18 reliable items can potentially be used to differentiate walkability.