Brightness-to-luminance (B/L) ratios based on the CIE 1924 V (lambda) for 195 test stimuli equally sampled from rite whole area of the CIE1976(u＇, v＇) chromaticity diagram were measured for four color normal observers, The results of two observers were similar to results in previous studies in that the B/L ratio increases as purity of the stimulus increases. However the results of the other two observers showed very low B/L ratios, especially in the reddish region. The B/L ratios based on each observer＇s sensation luminance were also calculated. Although the contour lines of equal B/L ratio became less atypical for the latter two observers, they still showed low B/L values compared to typical results. Large individual differences of the B/L ratio in the whole area of the chromaticity diagram Were indicated