Mania is a clinical state that could be described as sensation seeking behavior out of control. This article describes the biochemical correlates of the sensation seeking trait in normals including: gonadal hormones, monoamine oxidase, CSF norepinephrine, plasma dopamine-beta-hydroxylase and serotonin. The findings on monoamines and their neuroregulators in manic and depressed states of bipolar affective disorders are also discussed. Some hypotheses are suggested that link the personality disposition with the variations in the clinical state, and make some high sensation seekers 'at risk' for the affective disorder.