According to ‘Understanding the symptoms of schizophrenia’, patients with delusions of control and related symptoms seem unable to monitor their own actions normally. This idea bridges the gap between psychological accounts of symptoms and fundamental physiological processes in the brain. Delusions appear to result from a combination of an abnormal experience with a willingness to develop improbable explanations. Although drugs are not wholly satisfactory, the evidence of their value in treating acute schizophrenic episodes, and on a maintenance basis, is overwhelming. Discoveries about the processes underlying specific symptoms should assist the development of new drug treatments. Recently, however, interest has grown in developing psychological treatments targeting particular signs or symptoms.