We examined the efficacy, optimum dosage and adverse effects of levetiracetam in two prospective trials in children with epilepsy. In the add-on trial, 67 children between 6 months and 16 years were included. In the mono-therapy trial, 10 children between 4 years and 16 years were included. Levetiracetam was titrated up to an optimal dosage for every individual patient, depending on efficacy and tolerability, and reflecting clinical practice. The range of dosages used was between 12 and 62 mg/kg/day, with a median of 33 mg/kg/day. Overall, 20 weeks after the start of levetiracetam, there was a median seizure reduction of 60% (add-on trial 50%; mono-therapy trial 81%). Levetiracetam was equally effective for partial and generalized seizures. Side effects were less common in the mono-therapy trial. Tiredness (7.8%) and aggressiveness (5%) were the most common side effects, and were dose-related, but were no reason to discontinue levetiracetam. In 25% of the children, a positive effect was seen on behaviour and/or alertness. This could not be related directly to seizure control. Overall, these two clinical trials confirm that levetiracetam is a broad spectrum anti-epileptic drug with a favourable safety profile. The positive effect on behaviour needs further quantitative study.