The investigation of enzyme and neurotransmitter levels and/or their metabolites in the CSF of patients with senile dementia of Alzheimer's type (SDAT) could become a promising approach for a clinical research and diagnostic procedure. To learn more about the metabolic reflections of central metabolism in the CSF of patients with SDAT, we measured CSF levels of gamma-aminobutyric acid (GABA) and homovanillic acid (HVA), the dopamine metabolite. In 16 female patients with SDAT and in eight matched control patients, CSF GABA levels were measured by ion exchange with fluorimetric detection, and HVA levels were measured fluorimetrically. The GABA content of the CSF was significantly reduced in patients with SDAT, whereas the HVA level was unchanged.