We evaluated the efficacy and safety of lamotrigine in 41 children and young adults (age range, 3-25 years; mean, 12 years) with drug-resistant, partial epilepsies, based on a prospective, add-on study. Patients had severe symptomatic/cryptogenic partial epilepsies (mean seizure frequency = 3.6/day), resistant to one to four major antiepileptic drugs. Mean seizure frequency significantly decreased (P < .001) throughout the period of treatment. A good response (>50% seizure reduction) was observed in 15 patients of whom 6 were seizure-free (follow-up: 12-48 months). Higher responder rate was found among cryptogenic epilepsies and epilepsies symptomatic of cerebral malformation, whereas patients with posthypoxic-ischemic perinatal damage were poor responders. Lamotrigine discontinuation was mainly due to lack of efficacy (46% of patients), whereas only 2 patients developed a transient skin rash and did not drop out. Lamotrigine represents a valuable treatment for severe partial epilepsies of childhood that have proved resistant to previous antiepileptic drugs.