Genetic variants of red-cell acid phosphatase (ACP1), esterase D (ESD), transferrin (TF) and the group-specific component (GC) were investigated in schizophrenic patients with and without a family history of both schizophrenia and other psychiatric disorders. No evident association was found with respect to ACP1, TF and GC systems. A significant difference in the frequency of ESD heterozygotes was found between patients with and without a family history of schizophrenia.