The purpose of this study was to determine the usefulness of color vision screening in identifying patients with elevated digoxin levels (greater than or equal to 2.0 ng/ml). Test-retest color vision measurements were obtained on 56 subjects with elevated digoxin levels and 93 non-digoxin subjects. Two tests, the Ishihara and Sahlgren's Saturation Test (SST), identified digoxin levels of 2.9 ng/ml or more. These tests also yielded a high percentage of improved retest scores among subjects with elevated digoxin levels (greater than or equal to 2.7 ng/ml) of more than 4-days duration and a low percentage of improved retest scores among the non-digoxin group. The Ishihara, SST, and other bedside color vision tests may prove useful in the routine monitoring of patients on digoxin therapy, especially those with a high risk for toxicity.