Genetic factors appear to play a role in the etiology of schizophrenia, although no specific genetic mechanism has yet been identified. As a preliminary measure in the search for the chromosomal location of a gene or genes relevant to this illness, cytogenetic screening of populations of patients might provide clues for further in depth molecular studies. Additionally, since the X chromosome has been implicated as a possible site, specific examinations aimed at identifying abnormalities in this chromosome including the presence of the fragile X site, could also be important. The following report reviews the previous literature on chromosomal aberrations in schizophrenia and presents data from a new survey of 46 unrelated male patients with schizophrenia. No chromosomal aberrations or folate-sensitive fragile sites were found in samples from these patients.