We present a patient with myotonic dystrophy (MD) who was anesthetized with propofol using a target-controlled technique for electrophysiologic examination and cardiac catheter ablation. The patient became apneic unexpectedly at the same time when he fell asleep, with effect-site propofol concentration of 1.6 microg ml(-1). We had to insert a laryngeal mask airway (LMA), and mechanical ventilation was performed. The patient opened his eyes on verbal command at an effect-site concentration of 1.2 microg ml(-1) after the procedure. This concentration (1.2 microg ml(-1)) was slightly lower than our institutional average for adult male patients (1.5 +/- 0.2 microg ml(-1)). However, the time from the end of anesthesia to the patient's awakening was about 10 min. We considered that emergence from anesthesia was not delayed in this case. Careful titration of propofol by target-controlled infusion (TCI) enabled to evaluate the patient's sensitivity to propofol. We conclude that TCI of propofol was a useful anesthetic technique in the MD patient. Respiratory depression might occur in MD patients at low propofol concentrations. Precise control and titration over target propofol concentration is important in anesthetic management for MD patients.