BACKGROUND Rocuronium (Org 9426) was shown to have the fastest onset of action of all currently available non-depolarizing neuromuscular blocking drugs and to provide intubating conditions similar to those of suxamethonium 60 to 90 s after administration. We compared the intubating conditions after rocuronium and suxamethonium following rapid-sequence induction of anaesthesia. METHODS Fifty unpremedicated patients of ASA physical status I or II, scheduled for elective surgery were studied. Anaesthesia was induced with thiopentone 6 mg kg-1 followed randomly by suxamethonium 1 mg kg-1 or rocuronium 0.6 mg kg-1 and, 45 s later, intubation was commenced. Muscle fasciculations, intubating conditions and intubation time, haemodynamic variables and oxygenation were assessed. RESULTS Intubation time did not differ between suxamethonium (9.8 +/- 2.2 s) (mean +/- SD) and rocuronium (10.5 +/- 2.9 s), respectively. Intubating conditions were clinically acceptable (good or excellent) in all patients given suxamethonium and in 96% of the patients given rocuronium. However, the condition of the vocal cords was better (P < 0.05) and diaphragmatic response to intubation was less pronounced with suxamethonium (P < 0.05). Changes in heart rate and arterial blood pressure were similar in both groups. CONCLUSIONS The authors conclude that rocuronium is a suitable alternative to suxamethonium for rapid tracheal intubation even under unsupplemented thiopentone anaesthesia, at least in elective, otherwise healthy patients. Its use for rapid-sequence induction under emergency conditions, however, needs further investigation.