This study explored the nature of abstract thinking disorder in schizophrenia and brain damage. Previous research suggests that two deficits, inability to abstract and autism, interfere with the proverb interpretations of schizophrenic and brain-damaged patients. In the present study, an attempt was made to isolate the specific nature of abstraction deficit by dividing the abstracting process into two components: the translation of concrete stimuli into abstract elements and their integration into general principles. The scores of process schizophrenics, reactive schizophrenics, brain-damaged patients, and psychiatric controls on measures of translation ability, integration ability, and autistic interference with each were compared both before and after the groups were matched for intelligence and demographic variables. Although the schizophrenic and brain-damaged groups showed less ability to translate and integrate than the controls, these weaknesses reflected demographic differences, not disorder-specific deficits. Autistic interference with integration was also more apparent in the schizophrenics and organics than in controls and was also attributable to low intelligence rather than a specific defect. However, greater autistic interference with translation was found in the reactive and organic patients than in the controls or, apparently, the process schizophrenics, both before and after the effects of intelligence and demographic variables were controlled. Therefore, autistic interference appears to be a disorder-specific deficit in reactive and brain-damaged groups.