Although hallucinations occur in a range of organic and psychiatric conditions, they are not invariably a sign of illness and also occur in "normal" individuals. Evidence indicates that psychotic hallucinations lie on a continuum with normal experiences, and many more people experience hallucinations than meet criteria for clinical psychosis. In addition to a symptomatic continuum between normal individuals and patients with psychosis, there is evidence that hallucinatory experiences in nonclinical and clinical samples may share the same underlying etiologic influences, including sociodemographic risk factors and neurocognitive mechanisms. Predictors of patient status include beliefs about hallucinations, negative mood, and perceived lack of control.