Watershed assessment requires techniques capable of synthesizing large quantities of spatial information. Fuzzy logic is one approach for addressing this problem. Geographic information systems (GIS) have the capacity to represent and integrate several levels of information on watershed characteristics and condition. Spatial analyses can show the relative condition of a watershed or delineate zones requiring different levels of protection related to a set of activities. One of the disadvantages of techniques commonly used in these analyses (e.g. Boolean, Weighted Index, Analytical Hierarchy Process) is that they do not include the uncertainty of a given factor or in the final results, which can be addressed with a fuzzy logic approach. With fuzzy logic a fuzzy membership function is defined for each environmental factor, which defines a region where the inclusion or exclusion of the factor is unclear. This paper briefly reviews the approach and application of fuzzy logic to the Riparian Restoration Ranking (R3) System on several montane watersheds in Arizona.