Preliminary data are presented on levels of plasma cortisol, dopamine (DA), epinephrine (EPI), and norepinephrine (NE) before and after dexamethasone in 22 depressed patients (of whom 4 were psychotic). Platelet monoamine oxidase (MAO) activity, determined in 19 of the depressed patients, was significantly higher in the 4 psychotic patients than it was in the 15 nonpsychotic patients. Positive correlations were observed before and after dexamethasone among cortisol, DA, EPI, and platelet MAO. After dexamethasone, plasma NE correlated negatively with DA, EPI, and cortisol. The various correlations were due largely to the inclusion of the psychotic depressive subgroup. Data are also presented on the relationships between these biological measures and specific signs and symptoms.