To investigate whether volume reduction of the hippocampal formation of schizophrenics, as described previously, is paralleled by loss of neurons and fibre systems, tissue volumes and cell numbers of all parts of the hippocampal formation in post mortem brains of 13 schizophrenics and 11 age-matched controls belonging to the Vogt collection were determined. Volumes of the whole hippocampal formation (P less than 0.01), the whole pyramidal band (P less than 0.001) and the hippocampal segments CA1/CA2 (P less than 0.01), CA3 (P less than 0.005), CA4 (P less than 0.01) were decreased, whereas no significant volume reduction of the alveus and fimbria hippocampi and prosubiculum/subiculum could be found. The perforant path showed a trend towards volume reduction (P less than 0.1). The absolute number of pyramidal cells (tissue volume X cell density) was diminished in CA1/CA2 (P less than 0.05), CA3 (P less than 0.05) and CA4 (P less than 0.05), but was not significantly changed in the prosubiculum/subiculum, the presubiculum/parasubiculum and the granular cell layer of the dentate fascia. Pyramidal cell loss in CA1/CA2, CA3, CA4 was more distinct in the paranoid patients than in catatonics. The findings are discussed with respect to current hypotheses of limbic dysfunction in schizophrenia.