Cancer might be expected to be more common amongst schizophrenics than the general population. They frequently live in selenium deficient regions, have seriously compromised antioxidant defense systems and chain-smoke. The available literature on the cancer-schizoprenia relationship in patients from England, Wales, Ireland, Denmark, USA and Japan, however, strongly suggests that the reverse is true. One of the authors (Hoffer) has treated 4000 schizophrenics since 1952. Only four of these patients has developed cancer. Since low cancer incidence has been recorded amongst patients treated by both conventional physicians using pharmaceuticals and by orthomolecular doctors who emphasize vitamins and minerals, it follows that this depressed cancer incidence must be related to the biochemistry of the disorder itself. Taken as a whole, therefore, the evidence seems to suggest that schizophrenics, their siblings and parents are less susceptible to cancer than the general population. These relationships seem compatible with one or more genetic risk factors for schizophrenia that offer(s) a selective advantage against cancer. There is experimental evidence that appears to support this possibility. Matrix Pharmaceuticals Inc. has received a US patent covering the composition of IntraDose Injectable Gel. This gel contains cisplatin and epinephrine (adrenaline) and is designed to be injected directly into tumour masses. Cisplatin is a very powerful oxidant which will almost certainly rapidly convert the adrenaline to adrenochrome. While the manufacturers of IntraDose consider cisplatin to be the active cytotoxic agent in IntraDose, it seems more likely that adrenochrome and its derivatives may, in fact, be more effective. IntraDose gel has undergone or is undergoing a series of Phase III open-label clinical studies, being injected into patients' tumours that have been identified as the most troublesome by their physicians. The results have been impressive for breast cancer, malignant melanoma, esophageal cancer and cancer of the head, neck and liver. The evidence suggests that there are balanced morphisms in schizophrenia that result in above normal exposure to catecholamine derivatives. Since such catecholamines are both hallucinogenic and anticarcinogenic abnormally high exposure to them simultaneously increases susceptibility to schizophrenia and reduces the probability of developing cancer. These observations have significant implications for the treatment of both illnesses.