A slide viewing technique designed to assess spontaneous nonverbal expressiveness was administered to 37 male patients including 8 left hemisphere damaged (aphasic), 10 right hemisphere damaged, 9 Parkinson's disease, and 10 non brain-damaged (control) patients. Patients watched different types of affective slides while their facial/gestural responses were videotaped. Judges watching the video tapes without audio guessed the types of slide being viewed. Results indicated that aphasic patients were equal to or more expressive than controls, while right hemisphere damaged and Parkinson's disease patients were less expressive. The possibility that spontaneous non verbal expressiveness is mediated by the right cerebral hemisphere, with the left hemisphere playing an inhibitory role, was discussed as a tentative explanation.