This paper reviews the current status of the adrenochrome theory of schizophrenia. An account is first given of all the experiments in which adrenochrome was reported to induce psychotomimetic effects in normal volunteers. Then the evidence is presented that adrenochrome may actually occur in the brain as a metabolite of adrenaline in the C2 group of adrenergic neurons in the medulla, together with an account of current ideas of the function of these neurons in higher limbic functions. Lastly the recent evidence is reviewed that the gene for the enzyme glutathione S-transferase is defective in schizophrenia. This enzyme detoxifies adrenochrome.