Overall, >50% of patients achieved > or =50% seizure reduction. More important, 11% of patients were seizure-free for > or =3 months at the last visit; 10% of patients were seizure free for > or =6 months at the last visit. This robust therapeutic response was consistent for patients receiving TPM dosages >400 and <400 mg/day. The most commonly reported adverse events were related to the central nervous system. Over the 2.2-year treatment period, 19% of patients discontinued TPM therapy because of inadequate seizure control; 32% discontinued because of adverse events. Findings from this study show that TPM is a useful agent for long-term seizure control, with some patients becoming seizure free for extended periods despite failing previous AED therapy.