Eleven adult patients with severe head injuries caused by blunt trauma, (Glasgow Coma Score of eight or less after resuscitation), were studied while being mechanically ventilated and sedated in the intensive care unit (ICU). In a double blind randomized cross over trial each patient received a bolus of suxamethonium (1 mg kg-1) or an equal volume of saline (0.02 mL kg-1) before planned physiotherapy. Intracranial pressure (ICP) and mean arterial pressure (MAP) were measured continuously for 10 min after each injection. There were no significant changes in intracranial pressure or cerebral perfusion pressure (CPP) following the administration of suxamethonium or saline. Suxamethonium appears to be a safe drug to use on sedated persons with severe head injuries following blunt trauma.