We evaluated the visual field pattern with Blue-on-Yellow perimetry in 22 eyes of 22 persons with ocular hypertension. Another series of 20 normal eyes served as controls. All the subjects underwent central field perimetry with a Humphrey automated perimeter (Model 640) using White-on-White targets. Blue-on-Yellow perimetry was performed within one week later. Both groups showed no difference in White-on-White perimetry, but the ocular hypertensive group showed a diffuse reduction in central sensitivity to Blue-on-Yellow perimetry by an average of 2.5 dB compared with the controls. These findings show the possibility that ocular hypertension causes fragility of the blue-yellow transmission system including the blue cones.