The importance of monitoring and assessment of rangeland systems is generally accepted, buteh importanc eand benefits of monitoring based on a foundation of ecological site potential is less well understook. The concept of ecological sitesand their current implementation via NRCS ecological site descriptions and associated GIS spatial data layers provides a robust and scalable framework for rangeland monitoring and assessment. An ecological site provides a standard reference for land management, research and monitoring. The ecological site description informs managers as to what kinds of changes can be expected in response to management or disturbance and provides a reference for the interpretation of monitoring and assessment data. In addition, there are many practical uses of ecological sites for designing programs and collecting and analyzing data for rangeland monitoring and assessment. In this paper we describe a monitoring and assessment framework based on ecological sites and present examples for several current and potential applications of ecological sites to rangeland monitoring and assessment.