Oral dantrolene causes a dose-dependent depression of skeletal muscle contractility. A 52-year-old man treated with oral dantrolene for spasticity after spinal cord injury was scheduled to undergo irrigation and drainage of a thigh abscess under general anesthesia. He had taken 50 mg oral dantrolene per day for 3 years. Under standard neuromuscular monitoring, anesthesia was performed with propofol, rocuronium, and sevoflurane. A bolus dose of ED₉₅ (0.3 mg/kg) of rocuronium could not depress T1 up to 95%. An additional dose of rocuronium depressed T1 completely and decreased the train-of-four (TOF) count to zero. There was no apparent prolongation of the neuromuscular blocking action of rocuronium. The TOF ratio was recovered to more than 0.9 within 40 minutes after the last dose of rocuronium. A small dose of oral dantrolene does not prolong the duration of action and recovery of rocuronium.