Purpose: In infants with frequent therapy resistant seizures (TRS-infants), clinical detection of pyridoxine-dependency (PD) or -responsiveness (PR) occurs by empirical intravenous (IV) pyridoxine administration during recording of the EEG. However, in undiagnosed TRS-infants it is stilt unclear to what extent EEG alterations by pyridoxine-IV are attributable to PD/PR or to non-specific responses. Before EEG alterations by pyridoxine-IV can be ascribed to PD/PR, these non-specific responses should be excluded first. Methods: In 10 TRS-infants under 1 year of age, we determined the EEG effect by pyridoxine-IV on the EEG-recording. Results: After pyridoxine-IV administration, our data indicate declined (10-15%; p <0.05) EEG-amptitudes and total power (magnitude/frequency-band) at frontal, central and centro-temporat electrodes. Conclusion: In TRS-infants, pyridoxine-IV affects EEG-amptitude and -total power in a non-specific way, which does not identify PD/PR. (C) 2007 British Epilepsy Association. Published by Elsevier Ltd. AR rights reserved.