Objective: To determine whether divalproex sodium (DVPX) was superior to lithium carbonate ([Li.sup.+]) in the maintenance monotherapy treatment of youths diagnosed with bipolar disorder who had been previously stabilized on combination [Li.sup.+] and DVPX ([Li.sup.+]/DVPX) pharmacotherapy. Method: Youths ages 5-17 years with bipolar I or II disorder were initially treated with [Li.sup.+]/DVPX. Patients meeting remission criteria for four consecutive weeks were then randomized in a double-blind fashion to treatment with either [Li.sup.+] or DVPX for up to 76 weeks. Study participation ended if the subject required additional clinical intervention or if the subject did not adhere to study procedures. Results: Patients were recruited between July 1998 and May 2002. One hundred thirty-nine youths with a mean (SD) age of 10.8 (3.5) years were initially treated with [Li.sup.+]/DVPX for a mean (SD) duration of 10.7 (5.4) weeks. Sixty youths were then randomized to receive monotherapy with [Li.sup.+] (n = 30) or DVPX (n = 30). The [Li.sup.+] and DVPX treatment groups did not differ in survival time until emerging symptoms of relapse (p = .55) or survival time until discontinuation for any reason (p = .72). Conclusions: DVPX was not found to be superior to [Li.sup.+] as maintenance treatment in youths who stabilized on combination [Li.sup.+]/DVPX pharmacotherapy. J. Am. Acad. Child Adolesc. Psychiatry, 2005;44(5):409-417. Key Words: bipolar disorder, lithium, divalproex sodium.