Clusters of atypical absence, myoclonic seizures and tonic seizures developed in a thirteen-year-old boy with Lennox-Gastaut syndrome. As conventional antiepileptic drugs failed to eliminate the seizures, we treated the patient with continuous intravenous lidocaine (4 mg/kg/hr). The treatment reduced the duration of paroxysmal discharges (spike-wave complexes and rapid rhythm) from 3 sec/min to 0.7 sec/min, monitored by EEG. Oral mexiletine (5.4 mg/kg/day) following the lidocaine treatment has maintained good seizure control for two years with no adverse effects, and improved his behavioral problem. The treatment with lidocaine followed by mexiletine was useful for controlling clusters of intractable seizures.