The level of cerebrospinal fluid somatostatin-like immunoreactivity (CSF SLI) was determined for 11 chronic schizophrenic patients with moderate cognitive impairment and for 8 controls. The CSF SLI was significantly reduced (37%) in schizophrenic patients, but this decrease did not correlate with the degree of cognitive decline measured by the Mini-Mental State Examination, with psychotic symptoms estimated by the Brief Psychiatric Rating Scale, or with the neuroleptic dose. Although a reducing effect of long-term neuroleptic treatment cannot be totally excluded, the present study suggests that the CSF SLI level is decreased in cognitively impaired schizophrenic patients, as in many other disorders with cognitive impairment. © 1990.