From the literature and our experience, a relatively consistent picture of psychiatric and behavioral abnormalities in Wilson's disease emerges. The essential elements of this picture are as follows: 1. Psychiatric and behavioral abnormalities are frequent manifestations of WD. The estimates range from 30% (18) to 100% (2) of symptomatic patients. As Wilson himself was the first to state in reference to "mental change," "its importance should not be underestimated." 2. Psychiatric and behavioral abnormalities are often the initial manifestations of WD. Two thirds of our patients first presented with psychiatric symptoms and one third received psychiatric treatment before the diagnosis of WD was made. In the early stages of the disease, when psychiatric and behavioral symptoms predominate, the diagnosis is often missed. Of our 124 patients, WD was diagnosed in only one during this phase. Until the psychiatric presentation of WD is recognized, and the disease is included in the differential diagnosis of psychiatric symptoms, its diagnosis will be missed or delayed. In our patients, and others' (13,15), the delay in diagnosis ranged from 1 to 5 years. Such a delay is particularly tragic as favorable outcome depends upon early discovery. 3. The most common of the psychiatric and behavioral manifestations of WD include: personality changes such as irritability and low threshold to anger, depression sometimes leading to suicidal ideation and attempts, deteriorating academic and work performance that is present in almost all neurologically affected patients. We (1) have also observed, as did Scheinberg and Sternlieb (2) that WD patients exhibit increased sexual preoccupation and reduced sexual inhibition. Finally, cognitive impairment, psychosis, anxiety, and other psychiatric disorders, although less frequent, also occur. 4. Some of the psychiatric and behavioral symptoms are reversible with WD-specific therapy, whereas others are not. We are impressed with the frequency with which the behavioral and "cognitive" symptoms are reversed over 1 to 2 years of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)