Summary The changes in the cerebrospinal fluid (CSF) β-endorphin (β-end) levels within 24 h following the trauma were examined in 45 patients with head injuries. CSF samples obtained from 25 healthy subjects who had minor surgical operations under spinal anaesthesia were included as the controls. Patients with head injuries were evaluated according to their Glasgow Coma Scale (GCS) scores on admission to the neurosurgery clinic and four subgroups were formed as follows: Group I: minor head trauma (GCS: 13-15) without skull fracture; Group II: mild head injury (GCS: 13-15) with skull fracture; Group III: moderate head injury (GCS: 8-12) and Group IV: severe head injury (GCS: <8). All patients with head injury had significantly higher CSF β-end levels than the controls (P< 0.001). The levels in patients with mild head injury (Group II) were significantly higher than those with severe head trauma (Group IV) (P< 0.001). There was not any correlation between the CSF β-end changes and the GCS scores of the patients. Endogenous opioid peptides are suggested to have a role in central nervous system (CNS) injuries. However, the CSF levels of β-end in patients with varying degrees of head trauma have not yet been clearly documented in the literature. In the present study, significant changes in CSF β-end levels are detected in patients with a wide range of head trauma (from minor head trauma to severe injury); however, the increased CSF β-end levels were not correlated to the early prognosis of the patients. © Pearson Professional Ltd 1996.