The effects of succinylcholine, which was given to facilitate tracheal intubation on the duration of action of subsequently administered vecuronium bromide, were evaluated in 54 adult patients who underwent abdominal surgeries under enflurane anaesthesia. The electromyographic response to train-of-four ulnar nerve stimulation was measured. Twenty-seven patients received 1 mg.kg-1 of succinylcholine, followed by 0.15 mg.kg-1 of vecuronium when the electromyographic response recovered to 50% of control after succinylcholine-induced neuromuscular blockade. The other 27 patients served as the control group, receiving 0.15 mg.kg-1 of vecuronium without prior administration of succinylcholine. In both groups, administration of supplemental 0.04 mg.kg-1 of vecuronium was repeated whenever the electromyographic response recovered to 25% of control during surgical procedures. The duration of blockade induced by the initial 0.15 mg.kg-1 of vecuronium was 56.5 +/- 12.8 (mean +/- s.d.) min for the group with succinylcholine, and 58.5 +/- 21.5 min for the control group. In both groups, the average duration of four consecutive supplemental doses of vecuronium was approximately 35 min. No significant differences between groups were found in the duration of neuromuscular blockade induced by initial and supplemental doses of vecuronium.