A group of 14 patients with isolated visual hallucinations who met the criteria proposed by Gold and Rabins for Charles Bonnet syndrome (with the exception of the criterion "hallucinations are stereotyped") underwent psychiatric, neurologic, and ophthalmologic tests. Additional common characteristics of the hallucinations included the absence of personal meaning of the content of the hallucinations and the disappearance of the hallucinations when the patients closed their eyes. There was no evidence for a relationship of the syndrome to psychiatric disorders. In the majority of cases, ocular pathology and neurologic disturbances were diagnosed. There was also evidence that most patients were suffering from social isolation. From these data it is concluded that a combination of factors is probably responsible for the Charles Bonnet syndrome.