Treatment of epilepsy with medication is a major part of the overall management of patients with epilepsy. We will discuss here three aspects of the follow-up of those patients; adverse events of treatment, assessment of response to treatment and biological follow-up. Adverse events associated with the therapy are not infrequent since they are reported by half of the patients. Since seizures occur mostly in an aleatory way, it is important to consider the duration observed in the assessment. A relative decrease of the seizure frequency must be interpreted cautiously as regression to the mean is frequent in the spontaneous fluctuations of the seizure frequency. Biologic follow-up is mostly helpful with older generation antiepileptic drugs.