We have evaluated the effects of a single bolus dose of rocuronium 0.6 mg kg-1 (group 1, n = 10) or vecuronium 0.1 mg kg-1 (group 2, n = 10) on intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP) and heart rate (HR) in 20 neurosurgical patients undergoing mechanical ventilation of the lungs during continuous sedation with sufentanil and midazolam. Before and after neuromuscular block using twice the ED90 of the blockers, ICP, MAP, CPP and HR were recorded continuously for 15 min. Treatment caused no significant changes in ICP, CPP or MAP and there was no evidence of histamine release. Mean maximum block in the rocuronium group was slightly less than that in the vecuronium group (95.9 (3.1)% vs 100%; ns) The difference between the two groups in onset time (rocuronium 142 (62) s, vecuronium 192 (64) s; P = 0.04) was significant. Patients in the rocuronium group showed a slight (7(4)%) but significant (P = 0.003) increase in heart rate.