Recent developments in microcomputer technology have resulted in the widespread availability of workstations with large memories, high processor speeds, and graphical displays. Because of the large number of applications in computer aided design and document preparation, most of the utilities which have been written for these workstations are designed to display wire-frame figures, shaded graphics models, or text. Such tools are not suited to the special needs of image processing. This paper describes displaytool, a utility which provides a window-based image display environment tailored for image processing. Displaytool supports subplane selection for multidimensional images; a large pixel value range, including negative values; interactive manipulation of colormaps for continuous contrast and brightness adjustment; statistical image summaries with graphical histogram display; interactive image subtraction; and simultaneous display of multiple images with arbitrary overlapping. The program runs under UN/X1 on Sun workstations within the Suntool window environment.