The objective of this paper is to clarify the effect of spectral power distribution of different fluorescent lamps on the human brightness perception in a building interior. The following psychological tests were conducted : The warm white, daylight and 3band-type fluorescent lamps were used as lighting sources. The 22 subjects compared lit environments of a pair of rooms. One was lit by daylight fluorescent lamps and the other room was lit by the warm white or 3band-type fluorescent lamps, respectively, at three luminance level : 100, 200 and 300cd/m^2. After the subjects judged the brighter room, they adjusted one side to get equal brightness with the other. At that condition luminance data of two rooms were recorded. Ratios of luminance by the compared lamp to that by daylight lamp were calculated. For all subjects, the ratios 1.22 and 1.03 were determined for the warm white and 3band-type fluorescent lamps, respectively, to obtain the equal perceived brightness at luminance level 100cd/m^2. The ratio decreases with a rise in luminance level.
