The concentration of homovanillic acid (HVA) in the lumbar cerebrospinal fluid (CSF) of 18 patients with endogenous depression was significantly lower than that of 18 neurological controls not affected by extrapyramidal diseases, epilepsy, senile or presenile dementia. The 5hydroxyindoleacetic acid (5-HIAA) was also decreased in the depressed group but not significantly so. These data support the concept of an involvement of dopamine metabolism in affective disorders. After one week of treatment with dexamethasone (0.75 mg, daily) no significant change was observed in HVA or 5-HIAA levels in the CSF; after two weeks of imipramine hydrochloride (50 mg, three times a day) 5-HIAA, but not HVA, was significantly reduced. No negative correlation was found between levels of HVA or 5HIAA and scores on the Hamilton and Beck Rating scales for various symptoms of depression. Age was also not correlated with HVA or 5HIAA.