This thesis examined the effects of luminance contrast, raster modulation, and ambient illumination on readability and image quality of text presented on a CRT display. Participants read a Tinker Speed of Reading text passage on the monitor and then responded when they found the out-of-context word in the passage. Correct responses and response times were recorded. Participants also rated the image quality of the monitor by selecting a number between one (worst imaginable) and nine (best imaginable). An ANOVA revealed that luminance contrast significantly affected errors. It is suggested that luminance contrasts of 7:1 be used to maintain low error rates. None of the independent variables affected the time required to read the Tinker passages. However, luminance contrast, raster modulation, and illumination significantly affected the subjective quality ratings. Participants rated the 3:1 luminance contrast, the 1.2 RAR, and the 1000 lux ambient illumination conditions as possessing the lowest image quality. From this research, it can be concluded that 7:1 is the preferred contrast ratio. This conclusion is based upon the findings that the 3:1 and 7:1 luminance contrast conditions produced the fewest errors and the 5:1 and 7:1 luminance contrast conditions produced the highest subjective image quality ratings. This recommendation holds over a RAR range of 0.8 to 1.2 and an ambient illumination range of 10 to 100 lux. High illumination levels would require special attention due to the low image quality ratings for the 7:1/1000 lux interaction. / Master of Science