A common polymorphism in the alpha1-antichymotrypsin (ACT) gene is associated with Alzheimer's disease. ACT is also a trophic factor in the hippocampal neurons. In order to examine if the ACT gene plays a role in the pathogenesis of schizophrenic disorders, patients (n = 175) and control subjects (n = 114) were genotyped for ACT. We also investigated the relationship between genotypes and patients' cognitive function as evaluated by the Clinical Dementia Rating Scale and the Mini-Mental State Examination. The results demonstrated no association between schizophrenia and/or cognitive deficit in schizophrenia and ACT polymorphism. The data suggest that the ACT gene is not of major importance for the genesis of schizophrenia. Further studies measuring ACT expression as messenger RNA or serum ACT level may help to exclude the role of ACT in the pathogenesis of schizophrenia.