To determine if serum prolactin levels were correlated with the level of depression in an ambulatory medical clinic population, prolactin was measured by immunoassay in all new medical patients completing the Langer Scale and the Popoff Index of Depression. Thirty-four of 71 patients (48%) were found to be depressed with a positive Popoff Scale. There was no difference in the prolactin levels in the depressed and nondepressed patients, who were matched for age and sex. Thus, depression, as seen in an ambulatory medical population, is not associated with increased prolactin release.