The primary objective of this study is to determine the maximal tolerated dose (MTD) of E2007 given twice daily (bid) or once a day (qd) in patients with refractory partial-onset seizures (including secondarily generalized seizures). The secondary objectives are to evaluate the safety, efficacy, concentration-efficacy relationship, and pharmacokinetics of E2007 and the effects of E2007 on the Profile of Mood States (POMS) test.