A side effect associated with the use of some antiepileptic drugs (AEDs) is change in body weight. To evaluate the effect of lamotrigine on body weight in adult patients with epilepsy, we conducted a retrospective review of data from 463 patients treated with lamotrigine in 32 clinical trials. Mean daily dose was 259 (+/-155) mg and duration of therapy was 318 (+/-87) days. The mean change in body weight was 0.5 (+/-5) kg. Lamotrigine was associated with stable body weight in patients with epilepsy.