A Japanese girl with atypical pyridoxine-dependent seizures is reported. Until 9 months of age the seizures had been controlled by conventional anticonvulsants. The initial administration of pyridoxine was followed by a collapse; the suppression-burst pattern changed to an almost flat pattern in the EEG. T1- and T2-weighted magnetic resonance imaging (MRI) scans showed poor differentiation between white and gray matter, and T2-weighted MRI scans showed periventricular hyperintensity areas adjacent to the posterior horns of lateral ventricles. The findings in this patient indicate that pyridoxine should be given to infants with intractable epilepsy, regardless of the response to anticonvulsants, and that resuscitation facilities should be available during such a trial.