1. This study presents the results of the preliminary screening of vigabatrin as add-on therapy in an open, non-controlled multicentre study in children with refractory epilepsy. 2. There were 135 children, with an age range of 2 months-12 years. Main seizure type was partial in 42%, generalized in 29%, Lennox-Gastaut syndrome in 19% and West syndrome in 10%. 3. Vigabatrin was added onto current antiepileptic treatment in an initially recommended dose of 40-80 mg kg-1 day-1. However, the doses were frequently increased when tolerance allowed it, and the final mean dose used was 87 mg kg-1 day-1 (27-600). 4. A 75% to 100% reduction in seizure frequency was observed in 25% of patients (11 patients became seizure free) and 50 to 75% decrease in a further 13%. Efficacy was better in partial seizures, with good to excellent results in 49% of patients. The use of high doses, above 100 mg kg-1 day, was not associated with greater efficacy in this preliminary study. 5. No side effects were reported in 79% of patients. Agitation and insomnia were observed in 8.8% and somnolence in 6%. Other adverse events included ataxia (2.2%), nausea (2.2%) and increased appetite (1%). A moderate and transient decrease in haemoglobin was reported in six patients from the same centre; these patients were all receiving very high doses of vigabatrin (250 to 600 mg kg-1 day-1). 6. Vigabatrin thus appears to be a safe antiepileptic drug that may be effective in the treatment of severe epilepsy in children.