As computer usage has become more widespread, the number of complaints of visual discomfort and eye strain among computer operators has also increased. The temporal flicker of display screens can be a significant source of this visual discomfort. The purpose of this research was to determine how illuminance, luminance, screen test pattern, and viewing angle affect the perception of flicker in a CRT, especially in relation to the flicker evaluation method in the ANSI/HFS 100-1988 standard. Twenty participants viewed a CRT at different viewing angles, under different levels of illuminance and luminance, and with different screen test patterns. Two of the conditions matched conditions specified in the ANSIIHFS 100-1988 standard, while the remaining conditions represented additional levels of illuminance, luminance, and a different screen test pattern. For each condition, the display's refresh rate was manipulated in ascending and descending trials to determine the critical flicker frequency (CFF); the threshold point at which flicker was first noticeable (or not noticeable). An Analysis of Variance and post-hoc Newman-Keuls analyses were calculated to determine the significant effects on the CFF. The CFF values were higher with the higher illuminance and luminance values, and with the white screen viewed in the periphery. When compared with conditions specified in the ANSI/HFS 100-1988 standard, the additional levels of illuminance, luminance, and screen test pattern examined in this study are more representative of actual usage conditions and resulted in higher CFF values. Based on these results, it is concluded that the flicker evaluation procedure in the ANSIIHFS 100-1988 standard does not ensure flicker-free CRT viewing under typical office environment conditions. An alternative flicker evaluation procedure is proposed. / Master of Science