A set of schizophrenic male monozygotic triplets is described. At age 20 years, within 8 months the three men independently developed acute fulminant schizophrenic disorders (DSM-III-R) with auditory hallucinations, bizarre delusions, and thought disturbances. There were also great similarities between the triplets with regard to the chronic intermittent course of the disorder, impairment of social adjustment, and loss of working ability. The psychoses responded rapidly to conventional neuroleptic treatment. neuropsychological assessment demonstrated similar marked reductions of attentional, mnestic, and executive functions. Magnetic resonance imaging (MRI) showed similar borderline ventricular enlargement and widened subarachnoid spaces over frontoparietal and basal regions as well as around the pituitary gland (empty sella). All the boys also had a right-sided hearing defect with a marked reduction of the ossicular bones on the right side. Possible clues as to etiological mechanisms were the lack of reported family history for the disorder and a possible influenza infection in the mother during the first trimester. It is suggested that a DNA aberration being present or occurring at conception initiated a precise timeprogrammed series of events that produced the very similar schizophrenic phenotypes. Such an aberration might have been induced by an external agent, occurred spontaneously, or been inherited by a recessive mechanism. It seems possible that the psychoses, the reductions of neuropsychological functions, the morphological MRI changes, and the right-sided ossicular reductions may all be related to such a DNA alteration.