We have compared intubating conditions at 60 seconds, onset times and reversal characteristics of the new steroidal nondepolarizing muscle relaxant rocuronium with atracurium and vecuronium. A dose of approximately 1.75 X ED90 of each agent was used to assess their relative suitability for brief day case dental procedures requiring intubation. The anaesthetic technique included propofol, fentanyl, nitrous oxide/oxygen and isoflurane. Electromyography was used to assess neuromuscular blockade. The percentage of good or excellent intubating conditions at 60 seconds was 80% for rocuronium but only 12.5% each for atracurium and vecuronium. The mean percentage block at 60 seconds was 55.1% for rocuronium, compared to 9.2% for atracurium and 8.3% for vecuronium. Rocuronium had the fastest onset time to maximum block (mean 313 sec) compared to atracurium (mean 391.9 sec) and vecuronium (mean 331.9 sec). The duration of action of rocuronium was shorter than either atracurium or vecuronium, times for spontaneous recovery to 75% block being 22.2 min, 29.6 min and 26.3 min respectively. The neostigmine evoked recovery indices were rocuronium 4.2 min, atracurium 6.6 min and vecuronium 3.7 min. Maximum blockade of greater than 97% was achieved with all three relaxants.