To find out whether ventricular enlargement in schizophrenia, as demonstrated by neuroradiological methods, is caused by an atrophy of ventricle surrounding diencephalic structures, volume measurements and linear measurements of the whole thalamus, all large thalamic subnuclei and some extrathalamic brain parts were carried out on serial sections of post mortem brains belonging to the Vogt collection. The only significantly diminished parameter of this study was the thickness of the periventricular grey matter surrounding the third ventricle, while the volume and linear measurements of the whole thalamus and all large thalamic subnuclei were not significantly changed. The findings are discussed with respect to current hypotheses of diencephalic dysfunction in schizophrenia.