BACKGROUND: Although the incidence of postoperative residual curarization (PORC) following the use of intermediate-acting neuromuscular blocking agents is lower than that of longer-acting neuromuscular blocking agents, it has been reported in many studies. We compared the incidence of PORC following either rocuronium or vecuronium given by intermittent bolus or continuous infusion dosing. METHODS: Ninety-eight patients were included in this study. Neuromuscular blocking drugs were administered based solely on clinical criteria, and the reversal agent pyridostigmine was given to all patients. Residual block following rocuronium infusion (Group R-I), rocuronium bolus (Group R-B), vecuronium infusion (Group V-I), or vecuronium bolus dosing (Group V-B) was evaluated on arrival in the postanesthesia care unit. Neuromuscular function was assessed acceleromyographically (using TOF-Watch(R) to measure the train-of-four (TOF) ratio) and also clinically. PORC was defined as a TOF ratio of < 0.8. RESULTS: The incidence of PORC on arrival in the postanesthesia care unit was 20% in Group R-I, 23% in Group R-B, 42% in Group V-I, and 19% in Group V-B. Mean TOF ratio in Group V-I was less than those of the other groups (P < 0.05). CONCLUSIONS: PORC is still common following vecuronium or rocuronium, even after the block is antagonized, if neuromuscular blocking agents are administered according to clinical criteria alone.