• Five patients had absence seizures refractory to treatment with either ethosuximide or valproate sodium. To determine their response to combination therapy with the two drugs, four of the five had serial 24-hour intensive monitoring studies that included cable telemetric EEG recording, closed-circuit television observation, and frequent antiepileptic drug (AED) serum level determinations. The resultant data confirmed the clinical and EEG effects of serial alterations in AED programs. All five became seizure free with combination therapy. Combination therapy with ethosuximide and valproate should be considered in patients whose absence seizures do not respond to standard therapeutic measures.