Eleven fit unpremedicated patients took part in the study. Group I (five patients) received atracurium 0.3 mg kg-1 and group II (six patients) received alcuronium 0.2 mg kg-1. The simultaneous recovery of respiration, judged by serial measurements of the tidal volume and blood-gas values, and peripheral neuromuscular function, judged by the response of the adductor pollicis muscle, were studied. Anaesthesia was maintained with 66% nitrous oxide in oxygen, supplemented by 0.5% halothane. The tetanic response reappeared 17.6 +/- 0.92 min (group I) and 19.2 +/- 2.6 min (group II) after the administration of the drug, and spontaneous breathing at 24.0 +/- 2.08 min (group I) and 23.6 +/- 2.1 min (group II). Adequate recovery of respiratory muscle function was present in group I within 15 min of the onset of spontaneous respiration, whereas in group II this recovery took 30 min. At this time there was marked peripheral neuromuscular blockade with the peak tetanic height value less than 25% of control in both groups. It was concluded that recovery of the respiratory muscles from neuromuscular block by atracurium and alcuronium occurred more rapidly than the recovery of the small muscles of the hand, but that adequate tidal volume, in the absence of other clinical signs, should not be regarded as a reliable indication of complete return of neuromuscular function.