Two groups of 20 agitated and retarded depressed psychiatric patients were compared with a group of volunteer controls. Clinical ratings and changes in electrodermal activity, digital pulse volume (DPV), reaction and movement times were studied during: (1) relaxation; (2) nonsignal sensory, and (3) signal sensory stimulation. All participants received two blocks of six randomized trials of visual and auditory nonsignal sensory stimulation, and three blocks of seven trials of signal sensory stimuli in a reaction time counterbalanced design. The results were: (a) basal skin resistance was significantly higher for both depressed groups; (b) number of spontaneous electrodermal responses failed to differentiate controls from depressed patients; (c) magnitude of skin resistance responsivity during nonsignal sensory stimulation was not significantly different among the three groups; (d) DPV changes did differentiate retarded depressives from controls and agitated depressed patients, and (e) mean visual, auditory and tactile reaction and movement times were significant discriminators between controls and depressed groups. Although the results of the present investigation support earlier studies of agitated and retarded depression, it is proposed that a more substantive issue in studying depression in future should be the elucidation of the mediation and production hypotheses of depressed patients.