Purpose. To investigate the possible dysfunction of monoamine metabolism in patients with early-onset, epileptic encephalopathies. Methods. The CSF dopamine, serotonin and biopterin metabolites were studied in 37 patients with severe, mostly drug-resistant epilepsy. Results. No significant abnormality was found, whatever the type of epilepsy, cryptogenic or symptomatic. Conclusions. The present study failed to demonstrate that dysfunction of the main neurotransmitters pathways is a common phenomenon in children with early-onset, severe epileptic encephalopathy.