The authors report the development of a color perimetry procedure which compares sensitivity of the short-wavelength color-vision mechanism in the peripheral visual field for normal eyes, eyes with ocular hypertension, and eyes with primary open-angle glaucoma. To isolate the short-wavelength cone mechanism, they modified an automatic projection perimeter to blue-on-yellow color perimetry and used a monochromatic 440-nm stimulus and a broad-band bright yellow background. The three groups of subjects were matched for age and lens density. Refraction, pupil size, acuity, and medication were controlled. Under these conditions, most glaucomatous eyes showed reduced sensitivities more than two standard deviations below normal. Normal control eyes were significantly different from eyes with ocular hypertension only in the superior nasal field (P less than 0.05), but normal eyes differed from eyes with primary open-angle glaucoma in all areas of the field (P less than 0.01).