Using a specific high-performance liquid-chromatographic method, we measured norepinephrine, epinephrine, and dopamine in 24-h urine collections from 459 men and 497 women, ages 17 to 88 years. We found a significant negative correlation between age and the 24-h excretion of dopamine in men and women (P less than 0.001). Epinephrine excretion decreased with age in men (P less than 0.001). No age dependence was observed for norepinephrine (P greater than 0.2). The excretion of all three catecholamines, expressed in nmol/24 h, was significantly greater in men than in women. The differences, however, were small. With data expressed in nmol/g of creatinine, only epinephrine excretion was greater in men; norepinephrine and dopamine excretions were slightly greater in women. Also, expressed in these units, urinary excretion of norepinephrine in both sexes and of epinephrine in women was significantly positively related with age; urinary excretion of dopamine was significantly inversely related to age in women, but not in men. Reference values are provided for age-independent variables in both sexes.