The correlation between the degree of psychopathology (assessed by the Minnesota Multiphasic Personality Inventory, MMPI) and sympathetic function (assessed by the skin potential response to somatosensory stimuli) was evaluated in 209 patients with affective disorders. A number of skin potential parameters (skin potential levels, negative fluctuations of first derivative of skin potential, negative areas in phase plane analysis, differences between last and initial average potentials and between the last average potential for the preceding stimulus and initial average potentials for a given stimulus) were correlated with the psychopathology index, calculated as the average of clinically relevant MMPI scales. Categorical classification of patients having or not having abnormally high psychopathology index scores also supported the differences in skin potential response between both groups of patients. The results further indicate the existence of a correlation between severity of mood disorders and increased sympathetic reactivity.