Altered activities of biogenic amine-related enzymes have been reported in some studies of patients with affective disorders and chronic schizophrenia. To evaluate whether any relationship between personality variations, including non-diagnosed psychopathology, and these enzymes might occur in non-psychiatric patients, 95 young adult volunteers were studied. Higher MMPI and Zuckerman sensation-seeking scale scores were found in male, but not female, volunteers with lower platelet and plasma amine oxidase activities. Males generally exhibited negative correlations, while females had positive correlations between the psychological test scores and amine oxidase activities. In contrast to the amine oxidase results, no associations were observed between plasma dopamine β-hydroxylase activities and the personality variables.