We measured plasma dopamine-β-hydroxylase (DBH) activity in depressed patients and normal controls. There were no significant differences for plasma DBH activity between depressed patients and controls nor between melancholic or nonmelancholic depressed patients nor between depressed patients who were nonsuppres-sors or suppressors according to the dexamethasone suppression test. Among the depressed patients plasma DBH activity correlated significantly with extraversion scores on the Eysenck Personality Questionnaire