Abstract Abnormalities in the hypothalamic–pituitary–adrenal axis (HPA) have been implicated in psychosis. To our knowledge, no prior study has measured pituitary volume in a neuroleptic-naïve schizophrenic population. Herein, we present data exploring the volumetric differences in a sample of antipsychotic-naïve patients with a DSM-IV diagnosis of schizophrenia versus appropriately matched healthy controls. Pituitary volumes were measured in 51 patients with schizophrenia (36 males, 15 females, mean age ± S.D.: 25.2 ± 7.4 years) and 55 healthy controls (30 males, 25 females; mean age ± S.D.: 25.2 ± 6.6 years) Measurements were conducted on 1.5 mm thick T1-weighted coronal images from a 1.5T scanner by two trained raters. Patients with schizophrenia had significantly smaller pituitary volumes than healthy control subjects (mean volume ± S.D. = 0.58 ± 0.14 cm 3 and 0.66 ± 0.17 cm 3 respectively; ANCOVA (using intracranial volume, gender and age as covariates), F = 6.81, df = 1, 101; p = 0.01). These findings provide new evidence of a smaller pituitary volume in neuroleptic-naïve patients with schizophrenia. The observed alterations in pituitary volume are consistent with neuroendocrine studies that have reported abnormalities in the HPA axis in psychosis. Similar volume reductions have been seen in other neuropsychiatric populations and may cut across diagnostic boundaries.