A 7 year-old boy had had partial complex seizures from the age 6 years. Two days after commencing a treatment by VPA in a daily dose of 55 mg/kg body weight, disturbances of consciousness became obvious. He was admitted to hospital two days later. The E.E.G. on admission showed bilateral delta activity. The plasma levels of VPA was 140 mg/l. Diazepam, 7 mg, was given intravenously. Four minutes later, the clinical state and the E.E.G. returned to normal. This observation supports the hypothesis that VPA may have a paradoxical epileptogenic effect in some types of epilepsy.