Several studies, including our own, have reported atrophy of the cerebellar vermis in some schizophrenic patients. A recent report by Courchesne et al (1988) of hypoplasia of a developmentally specific region of the cerebellar vermis in autism prompted us to hypothesize that the cerebellar "atrophy" in some schizophrenic patients may also have developmental origins. We measured the area of the vermal lobules in 30 male schizophrenics. Contrary to expectation, the patients as a group had consistently larger cerebellar structures than the controls. Patients with perinatal injury had smaller structures than the nonperinatally injured group, but these measures were still larger than in the control subjects. Patients without perinatal injury differed from controls, having larger lobules VI-VII (p less than 0.03). These preliminary findings tentatively suggest a role for developmental factors for cerebellar structures in schizophrenia. Further research is needed to clarify the cerebellar vermal changes observed in some schizophrenic patients.