Sixty-nine children, aged from 2 months to 16 years and suffering from different types of drug-resistant epileptic seizures, mostly complex partial and secondary generalised, were recruited in an open, uncontrolled, prospective study of treatment with vigabatrin (gamma-vinyl GABA). Following a 3-month baseline observation period, the initial dose of vigabatrin of 10 mg/kg per day was progressively increased up to a maximum of 140 mg/kg per day, in addition to the conventional concomitant therapy. Sixteen patients showed a > or = 50% reduction in seizure frequency compared with the baseline, with complete control of seizures in nine cases. In 14 other patients, no substantial change in seizure frequency was observed, although an improvement in psychological performance after vigabatrin treatment warranted further continuation of the drug. In 35 patients vigabatrin was discontinued because of lack of efficacy (22 cases) and/or increased seizure frequency (13 cases). The clinical and biological tolerance of vigabatrin was remarkably good.