Relationships between dose and plasma concentration of carbamazepine and its 10, 11-epoxy metabolite and/or their seizure activities have not been documented when co- administered with other antiepileptics. We have studied 7 patients extensively in a clinical trial. Plasma samples for all have been analyzed using a specific, sensitive and reproducible HPLC procedure for the parent compound and its metabolite, in the presence of other anticonvulsants. We have collated almost all the data and will begin with the evaluation of disposition changes as a fraction of time and other antiepileptics.