Objective: The treatment of pediatric bipolar depression has not been well studied. The authors wished to prospectively study the efficacy of lamotrigine as adjunctive or monotherapy in adolescents with bipolar disorder who were experiencing a depressive episode. Method: This was an 8-week open-label trial of lamotrigine with 20 adolescents ages 12-17 years (mean age 15.8; 7 boys, 13 girls) with diagnoses of bipolar disorder I, II, or not otherwise specified, who were experiencing a depressive episode. Lamotrigine was begun at 12.5 to 25 mg/day. Primary response criteria was a 1 or a 2 on the Clinical Global Impression-Improvement at week 8. A secondary criterion was at least a 50% decrease in Children's Depression Rating Scale-Revised scores. Results: Nineteen subjects completed the trial. The mean final dose was 131.6 mg/day. Seven subjects were taking other psychotropic medications. Sixteen subjects (84%) responded by primary criteria, and 12 (63%) responded to our secondary criteria. Eleven subjects (58%) were considered in remission at week 8. Young Mania Rating Scale and Overt Aggression Scale-Modified scores also decreased significantly during the trial. There was no significant weight change, rash, or other adverse effects during the trial. Conclusions: Adolescents with bipolar depression appeared to respond to lamotrigine treatment, whether as adjunctive therapy or monotherapy, with decreases in depression, mania, and aggression. Larger, placebo-controlled studies of lamotrigine are needed in this population. (Contains 2 figures and 2 tables.)