A Phase III Open-Label, Multi-Center, Long-Term Extension Study of Depakote ER in Subjects Who Either Completed or Prematurely Discontinued Due to Ineffectiveness From Study M02-488.

Inclusion Criteria: Subject and subject's legal representative have voluntarily signed and dated an IRB-approved informed assent form and an IRB-approved informed consent form, respectively, before any study-specific procedures or tests are performed; The subject was randomized into Study M02-488 and either completed the study or prematurely discontinued due to ineffectiveness; and The subject is male or non-pregnant, non-lactating female Exclusion Criteria Female, of childbearing potential, and not using an effective method of birth control (e.g., total sexual abstinence or contraceptives). Experienced a serious adverse event in Study M02-488 which the investigator considered "possibly" or "probably related" to study drug; or In the investigator's opinion, long-term treatment with Depakote ER for migraine prophylaxis is contraindicated. For any reason, subject is considered by the investigator to be an unsuitable candidate to receive divalproex sodium or to participate in this study.