Corticotropin-releasing factor (CRF), an endogenous neuropeptide, has been shown to coordinate endocrine, behavioral and autonomic responses to stress. However, while previous studies of cerebrospinal fluid (CSF) CRF in schizophrenia have not demonstrated significant differences compared to control groups, these studies have not examined the effects of symptom severity or antipsychotic medication. CSF CRF concentrations increased in 18 of 21 male schizophrenic (DSM-III-R) patients after maintenance haloperidol was replaced by placebo (P < 0.0001); there was also a trend for relatively greater increases in relapsers. CRF concentrations were not significantly related to severity of psychosis, depression, anxiety or negative symptoms. During haloperidol treatment, but not after medication withdrawal, worse childhood premorbid adjustment was associated with higher CSF CRF levels. Finally, in contrast to the positive correlation between CSF CRF and norepinephrine concentrations reported in depression, a negative trend was seen in this schizophrenic sample.