Technical Abstract: In this paper, we examine the potential of using a small unmanned aerial vehicle (UAV) for rangeland inventory, assessment and monitoring. Imagery with 8-cm resolution was acquired over 290 ha in southwestern Idaho. We developed a semi-automated orthorectification procedure suitable for handling large numbers of small-footprint UAV images. The orthorectified image mosaics had a geometric accuracy ranging from 1.5 m to 2 m. Object-based hierarchical image analysis was used to classify imagery of plots measured concurrently on the ground using standard rangeland monitoring procedures. Correlations between image- and ground-based estimates of percent cover resulted in r-squared values ranging from 0.86 to 0.98. Time estimates indicated a greater efficiency for the image-based method compared to ground measurements. Overall classification accuracies for the image mosaics were in the 83-88% range. Even under the current limitations of operating a UAV in the National Airspace, the results of this study show that UAVs can be used successfully to obtain imagery for rangeland monitoring, and that the remote sensing approach can either complement or replace some ground-based measurements. Details of the UAV mission, image processing and analysis, and accuracy assessment are discussed.