Determinations of biopterin (BP), homovanilic acid (HVA), glutamic acid (GTA), and glutamine (GT) levels in cerebrospinal fluid (CSF) obtained through a lumbar tap were performed in 20 parkinsonian patients in different stages of evolution and without medication. In patients with motor symptoms not related to Parkinson's disease (dystonia, dyskinesia and essential tremor) (n = 4). In 7 other neurological patients subjected to spinal tap for diagnostic procedures neurotransmitters were also determined and taken as control groups. In 14 of the patients with Parkinson's disease, the symptoms were evaluated using conventional scales (UPDS, NYPDS, NWPDS, Schwab and England, and Hoehn and Yahr scale). The amplitude and the frequency of tremor were quantitatively evaluated through a single plane accelerometer Grass SP-1, akinesia was measured through reaction time to auditory stimuli, and rigidity through the speed of lineal movement. Evaluations were performed with the patient not on any medication for 1 week and repeated 1 h after the intake of 250 mg of 200/50 L-dopa/carbidopa preparation (Sinemet) and on a different day after the intake of biperiden (Akineton) 6 mg/day. Differences in neurotransmitter or metabolites levels between Parkinson's disease and control groups were determined through an independent Student's t test. Correlation between severity of symptoms in the scales and for each individual symptom measured through the quantitative tests and the levels of neurotransmitters in CSF were evaluated through the Pearson correlation analysis test. Modifications in the motor performance after administration of Sinemet and Akineton, and the levels of neurotransmitters were indirectly determined. RESULTS. (1) There were significant differences between the levels of BP and GT in patients with Parkinson's disease and control groups, (2) lower GTA levels correlated with more severe rigidity and akinesia, and with the best response to the administration of L-dopa and may be an important marker for prognosis, and (3) lower levels of GT correlated with least akinesia, but not with tremor, which may indicate that the akinesia depends on other biochemical abnormalities besides dopamine depletion.