Accumulating data suggest that the antiepilepsy drug lamotrigine, which has been available for adult use for more than a decade, also confers broad-spectrum, well-tolerated control of epilepsy in children. The current study--the open-label continuation phase of several short-term clinical trials--was conducted to assess the long-term tolerability and efficacy of lamotrigine as open-label adjunctive therapy or monotherapy in pediatric patients for a variety of seizure types and syndromes including partial seizures, absence seizures, and Lennox-Gastaut syndrome. Clinic visits occurred every 24 weeks throughout the treatment period. A total of 252 patients under 16 years of age were enrolled in the study. The numbers of patients exposed to at least 48 weeks, 96 weeks, and 144 weeks of treatment with lamotrigine were 185 (73.4%), 119 (47.2%), and 60 (23.8%), respectively, for an average duration of exposure of 96.7 weeks. The most common adverse events considered by the investigator to be drug related were dizziness (9.1%), somnolence (7.9%), nausea (6.3%), vomiting (5.2%), and headache (5.2%). The most common serious adverse events (regardless of suspected cause) included pneumonia (3.0%) and infection (1.9%). Investigators judged that the overall clinical status of three-fourths of the patients had improved at treatment weeks 48 and 96 relative to prelamotrigine clinical status. Lamotrigine administered as monotherapy or adjunctive therapy for an average of 2 years (96.7 weeks) was well tolerated and effective in pediatric patients with partial or generalized epilepsy. These results complement and extend the large body of data demonstrating the tolerability and efficacy of lamotrigine with short- and long-term use in adults.