Color vision deficit in 26 eyes with normal-tension glaucoma (NTG) is compared with that in 21 eyes with primary open angle glaucoma (POAG) using the color perimetry method developed by Iijima et al. Subjects had visual field defects confined to either the upper or the lower hemifield as determined by conventional white-on-white perimetry, and the stage of disease was relatively early with an average mean deviation (MD) of -7 dB. Except for intraocular pressure, there were no significant differences between NTG and POAG subjects in age, refraction, MD, and mean total deviation for spared and damaged hemifield. In the spared hemifield, the incidence of blue-yellow abnormality was significantly different between the two diseases (P = 0.01); in only 11% of the present NTG eyes versus 52% of the POAG eyes in the present study. In the damaged hemifield, however, the blue-yellow abnormality was found in about 75% of the eyes, whether NTG or POAG. This finding may further shed light on the pathogenesis of open angle glaucoma.