Recently, the Stalker system has been developed as a high-resolution three-dimensional radar imaging system for the detection of concealed roadside explosive hazards. This system has shown considerable capability in distinguishing between true targets and false alarms using conventional processing techniques such as RX filtering on 2D projections of the data. In this paper, we develop an extension of these methods for use with 3D radar imagery. We show several different prescreening approaches for automatically marking potential target locations and describe an evaluation program called the Tiger scorer. We tested our approach on data collected at an arid U.S. Army test site.