This article focuses on the incidence of cancer in schizophrenic patients. We review the relevant studies, which show a diminished risk of cancer. This is partly a methodological artifact, but also appears to be a genuine phenomenon. Such is the case especially for chronic hospitalized male schizophrenic patients, who have a reduced risk of lung cancer. To a lesser extent the same holds true for male schizophrenic patients in general. We discuss several hypotheses which could help to explain these findings, such as immunological changes, which could be either inherent to schizophrenia, or be due to the use of neuroleptics. There appear to be no studies of genetic influences on the relationship between schizophrenia and cancer.