The interaction between mivacurium and succinylcholine when mivacurium was administered during the early recovery from succinylcholine block was studied in 30 children 2-12 years of age anaesthetized with propofolalfentanil-N2O-O2. Neuromuscular response was monitored by adductor pollicis EMG. Fifteen patients received 200 micrograms.kg-1 of mivacurium (Group M), and another fifteen received 1500 micrograms.kg-1 of succinylcholine followed by 200 micrograms.kg-1 of mivacurium when the first EMG response recovered to 5% of calibration value (Group SchM). Plasma cholinesterase (pChE) activity was normal in each patient. The recovery times following mivacurium did not differ between the two groups. Times required for recovery of the first EMG response from 25 to 75% of full EMG recovery were 3.6 +/- 1.0 (mean +/- SD) and 4.0 +/- 0.7 min for the Groups M and SchM, respectively. The time from administration of mivacurium to the recovery of train-of-four ratio 0.70 was 13.2 +/- 3.3 min for the Group M and 13.6 +/- 3.1 min for the Group SchM (NS). Thus, in patients with normal pChE activity preceding administration of succinylcholine did not influence the recovery of neuromuscular function from subsequent mivacurium.