• Levels of 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) in the CSF, and norepinephrine (NE), epinephrine (E), vanillylmandelic acid, normetanephrine, metanephrine, and MHPG in the urine, were measured in 151 hospitalized patients with affective disorders and in 80 healthy controls following a two-week drug-free period. Unipolar and bipolar depressed subjects differed only in NE and E levels. Compared with controls, depressed subjects had higher CSF MHPG levels, women had higher 5-HIAA levels, and men had lower HVA levels. All urinary metabolites were elevated in depression and mania, with the exception of MHPG. The patterns of NE-E differences discriminated among the forms of affective disorders. These data suggest an imbalance of monoamine transmission in depression, characterized by the hyperactive sympathetic nervous system and adrenal medulla. However, MHPG may not be the measure of choice to reflect this imbalance, necessitating measurement of total body monoamine output.