Twenty-four subjects were studied to determine the effect of a 12-week program of aerobic exercise on the rate of daytime aqueous humor flow. Exercise increased the maximum oxygen consumption from 36 +/- 1.6 (mean +/- SE) to 40 +/- 2.2 ml/kg/min. No changes in resting intraocular pressure (12.4 +/- 0.44 before and 12.2 +/- 0.36 mm Hg after) or resting aqueous flow (3.03 +/- 0.11 before and 3.06 +/- 0.13 mul/min after) were observed. We conclude that a moderate and short-term program of aerobic exercise conditioning does not have a clinically significant effect on the resting rate of aqueous humor flow in young, healthy human subjects.