BACKGROUND: Under normal conditions, excitatory amino acids are dynamically balanced with inhibitory amino acids. Excitatory amino acids have been implicated in perinatal brain injury. OBJECTIVE: To investigate differences in the levels of the excitatory amino acids glutamic acid and aspartic acid, and the inhibitory amino acid gamma-aminobutyric acid (GABA) in the cerebrospinal fluid (CSF) of children with spastic cerebral palsy or athetotic cerebral palsy. DESIGN, TIME AND SETTING: Case-control exploratory observation of neurotransmitter in patients. The experiment was performed in the Pediatrics Department of the Second Affiliated Hospital of Changsba Medical College, the Cerebral Palsy Center of Xiangtan Affiliated Hospital of South China University and the Pediatrics Department of Xiangya Hospital, between February 2006 and May 2007. PARTICIPANTS: We selected 27 children with cerebral palsy, including 13 with spastic cerebral palsy and 14 with athetotic cerebral palsy. We selected 10 patients who were not affected by any neurological disease as controls. METHODS: Two mL blood-free CSF was harvested between the third and fourth lumbar vertebrae of each patient after anesthesia, and stored at 70℃. One mL CSF was mixed with 10 mg sulfosalicylic acid and placed in ice-bath for 10 minutes, then centrifuged 2 000 g for 10 minutes. The supatant was collected for amino acid quantitation. MAIN OUTCOME MEASURES: The concentrations of glutamic acid, aspartic acid and GABA in the CSF were determined by high-performance liquid chromatography and fluorometric method. The correlation of glutamie acid, aspartic acid and GABA levels with muscular tension in children with cerebral palsy was analyzed using linear dependence. RESULTS: The concentration of GABA was significantly lower in both spastic cerebral palsy and athetotic cerebral palsy patients than in the control group (P < 0.01). Glutamic acid and aspartic acid were significantly higher in both cerebral palsy groups than in the control group (P < 0.05-0.01). The concentration of GABA was significantly decreased in spastic cerebral palsy patients compared with the athetotic cerebral palsy group (P < 0.05). Muscular tension was positively correlated with the concentration of glutamic acid in spastic cerebral palsy patients (P < 0.05) but there was no significant correlation between aspartic acid or GABA and muscular tension (P > 0.05). CONCLUSION: Spastic cerebral palsy and athetotic cerebral palsy patients exhibit an imbalance of excitatory amino acids and inhibitory amino acids in their CSF: an increase in glutamic acid and aspartic acid, and a decrease in GABA. Amino acid levels are different in the CSF in varied types of cerebral palsy.