This study was designed to compare the tracheal intubating conditions during a rapid sequence induction of anaesthesia using rocuronium 0.6 (n = 61) or 1.0 mg.kg-1 (n = 130) or suxamethonium 1.0 mg.kg-1 (n = 127) as the neuromuscular blocking drugs. Anaesthesia was induced with fentanyl 1-2 micrograms.kg-1 and thiopentone 5 mg.kg-1 (median dose) and intubating conditions were assessed 60s after the administration of the neuromuscular blocking drug by an observer unaware of which drug had been given. Intubating conditions were graded on a three-point scale as excellent, good or poor, the first two being considered clinically acceptable. The study was carried out in two parts. At the end of the first part a comparison between the two doses of rocuronium was carried out when at least 50 patients had been enrolled in each group. The results showed the intubating conditions to be significantly superior with the 1.0 mg.kg-1 dose of rocuronium (p < 0.01). Final comparison between the 1.0 mg.kg-1 doses of rocuronium and suxamethonium showed no significant difference in the incidence of acceptable intubations (96 and 97%, respectively). The incidence of excellent grade of intubations was, however, significantly higher with suxamethonium (80% vs. 65%; p = 0.02). It is concluded that rocuronium 1.0 mg.kg-1 can be used as an alternative to suxamethonium 1.0 mg.kg-1 as part of a rapid sequence induction provided there is no anticipated difficulty in intubation. The clinical duration of this dose of rocuronium is, however, 50-60 min.