A literature survey of studies relevant to display size is followed by discussions of display size geometry, size calculation equations and selection of display size for imaging displays. A display size study was done. Display size was varied by using small(5 x 5 ), medium (10 x 10 ) and large (15 x 15 ) film transparencies of side looking airborne radar (SLAR) pictures viewed on a light table. The targets, one per picture, were 12 airfields, 12 railroad yards, and 12 tank farms. All targets were adequate in size for easy visual examination, The observers were 72 SAC and TAC radar navigators. The only briefing information for each picture was the type of target to be detected. Each observer saw each scene only once. Target detection time was measured. No target was difficult for all observers, but some were difficult for some. Average response times on individual scenes were sometimes quickest on the small display, and sometimes quickest for the medium or large display. Airfield and railroad yards were found quickest on the small display, the size for which response to tank farms was slowest. The results demonstrate that, when sensor and display resolutions and target image size are adequate, the display size yielding the quickest target detection for unbriefed targets depends upon the type of target. Keywords; Human factors, Side looking radar, Target detection.