Twenty one eyes with primary open angle glaucoma were tested with standard (white stimulus-on-white background) and color (blue stimulus-on-yellow background) visual fields over a range of 6-26 mo. There was no significant increase in threshold between the initial and final standard fields overall or by quadrant (P less than 0.188, overall field). A significant increase in mean log thresholds for all areas of the color visual field (P less than 0.019, overall field) was found. Of the 21 patients, nine worsened by greater than 0.2 log units, two improved by greater than 0.2 log units, seven worsened by less than 0.2 log units, and three improved by less than 0.2 log units. When these same patients were matched to 21 normal eyes by age, lens density, and acuity they showed significantly reduced thresholds throughout their color visual fields (P less than 0.023). Whereas normal age-related increases in threshold for the short-wavelength system are only 0.10 log units per decade (n = 88), 10 glaucomatous eyes with increases of 0.14-0.75 log units were found within only 26 mo. The authors conclude that color visual fields may indicate significant change in visual function before it is apparent on standard visual fields.