The frequency of postoperative residual neuromuscular block following the use of the long-acting non-depolarizing muscle relaxants is high, and manual evaluation of the response to nerve stimulation does not eliminate the problem. In this prospective and randomized study we evaluated the hypothesis that perioperative use of acceleromyography would allow for a more rational and precise administration of the long-acting muscle relaxant pancuronium resulting in a decrease in 1) the incidence and severity of postoperative residual neuromuscular block, 2) the amount of pancuronium used, and 3) the time from end of surgery to tracheal extubation. Forty adult patients were randomized into two groups, one managed without the use of a nerve stimulator, the other monitored using train-of-four (TOF) nerve stimulation and acceleromyography. All patients were anaesthetized with diazepam, fentanyl, thiopentone, nitrous oxide, and in some patients halothane, and they all received pancuronium 0.08-0.1 mg kg-1 for tracheal intubation, and 1-2 mg for maintenance of neuromuscular block. Neostigmine 2.5 mg preceded by atropine 1 mg was administered for reversal. In the patients managed without a nerve stimulator, the trachea was extubated when the anaesthetist judged the neuromuscular function to have recovered adequately for upper airway protection and spontaneous ventilation. In patients monitored with acceleromyography, the trachea was extubated when the TOF ratio was above 0.70. In all 40 patients, TOF ratio was measured using mechanomyography immediately after tracheal extubation and the patients were evaluated for clinical signs of residual neuromuscular block.(ABSTRACT TRUNCATED AT 250 WORDS)