Eighty-four cataractous eyes of 52 consecutive patients and 81 normal eyes of 48 subjects were evaluated with a commercially availability glare tester. Tests results were compared to visual acuity determinations in the refracting lane for ability to predict vision outdoors under daylight conditions. Among cataract patients, predictability of the two methods of measurement was not significantly different when subjects faced away from the sun. Glare scores were significantly better predictors (nearly twice as predictive) of outdoor visual acuity among cataract subjects facing the sun. These results demonstrate that measurement of sensitivity to glare is an important clinical procedure for evaluating functional visual disability in cataract patients under glare-producing conditions.