Sixty-one pediatric patients (12-229 months of age) with refractory epilepsy were treated with vigabatrin [gamma-vinyl GABA (GVG)] in a 16-week, single-blind, add-on, placebo-controlled trial. Twenty-three patients (38%) showed a reduction of more than 50% in seizure frequency; 12 patients (20%) experienced a seizure increase; and the remaining 26 did not show significant differences between placebo and GVG treatment. Among the 216 patients who entered the long-term phase after having experienced more than 50% decrease in seizure frequency, 14 continued with the same degree of improvement after 2-11 months of follow-up (mean 7.7). GVG was particularly efficient in cryptogenic partial epilepsy. Conversely, nonprogressive myoclonic epilepsy tended to be aggravated. Agitation was the most commonly observed side effect, mainly at onset of therapy in mentally retarded patients, but was easily reversed by dose reduction. GVG is a promising drug in the treatment of refractory epilepsies of childhood.