The effects of bolus doses of phenoperidine 1-2 mg i.v. either alone, or combined with pancuronium 2-4 mg, were investigated in seven patients in traumatic coma. Phenoperidine alone significantly reduced mean arterial pressure (MAP) by a mean (+/- SEM) of 13.2 (+/- 2.8) mm Hg. Overall there was no significant change in intracranial pressure (ICP) despite the decreases in MAP and, consequently, cerebral perfusion pressure (CPP) decreased (14.0 +/- 2.4 mm Hg) on all but one occasion. In some instances these decreases were considerable (maximum 38 mm Hg). Similar results were obtained when phenoperidine was combined with pancuronium. These findings suggest that the bolus administration of phenoperidine and probably other opiates should be avoided in traumatic coma.