To discover the significance of changes in the extracellular concentration of brain ascorbate, we used linear sweep voltammetry to monitor the ascorbate signal. Recordings were made with carbon paste electrodes implanted in the striatum and hippocampus of anaesthetised and unanaesthetised rats under a variety of conditions. Intraperitoneal administration of excitatory amino acid transmitters, but not tyrosine or glycine, increased extracellular striatal ascorbate; similarly, microinfusion of L-glutamate beside striatal electrodes enhanced the ascorbate signal. Electrical stimulation of the perforant path increased the extracellular concentration of dentate ascorbate in the unanaesthetised, but not in the anaesthetised, rat. These results support our hypothesis that changes in the extracellular concentration of brain ascorbate monitored by voltammetry reflect the release of excitatory amino acids.