The purpose of this study is to compare the effectiveness and safety of two treatment regimens, topiramate as compared to phenytoin, in preventing seizures in patients with new-onset epilepsy who require rapid initiation of antiepileptic drug therapy. Reasons for requiring rapid initiation of treatment, rather than slowly increasing an antiepileptic drug to an effective dose, may include severe or frequent seizures, or high risk to the patient of recurrent seizures.