The secretion of aldosterone declines with age. We reported that sodium depletion increased urinary excretion of 18-hydroxycortisol (18-OH-F). To elucidate the effect of aging on urinary excretion of 18-OH-F, we measured urinary 18-OH-F in 30 normotensive subjects aged 20-70 yr. There were significant negative correlations between age and urinary excretion of 18-OH-F or of aldosterone (r = -0.49, r = -0.58, P < 0.05, respectively) but not of urinary free cortisol. These results suggest that angiotensin may contribute to chronic regulation of 18-OH-F.