A mentally retarded 23-year-old woman with myoclonic astatic epilepsy developed an abnormal posture of extreme forward flexion, called camptocormia, during valproate monotherapy. Camptocormia occurred concomitantly with an increase of the plasma valproate level from about 330 mumol/l up to 530 mumol/l. Four weeks earlier she had developed hepatopathy during a regimen of carbamazepine, lynestrenol and sodium valproate. Hepatopathy subsided after the cessation of carbamazepine and lynestrenol. Camptocormia improved within a week after the reduction of the plasma valproate level to about 300 mumol/l. Four months later reversible camptocormia was manifested again concomitantly with about the same plasma valproate levels as above. Accordingly, camptocormia is a dose-dependent side effect of valproate.