Linear sweep voltammetry with carbon-paste electrodes was used to record simultaneously changes in the extracellular concentration of ascorbic acid, uric acid and homovanillic acid (HVA) in the striatum of unanaesthetized rats. The ascorbate signal was used as an index of excitatory amino acid release, whereas the HVA signal reflects changes in dopamine release. Microinjection of 2-chloroadenosine depressed both the ascorbate and the HVA signals; the infusion of adenosine deaminase increased the amplitude of the two signals. These results, considered in the light of lesion + binding studies, suggest that released endogenous adenosine may modulate the release of transmitter from both corticostriatal and nigrostriatal terminals. The effect of adenosine deaminase on the urate signal provides preliminary evidence that changes in this signal may reflect variations in the release of adenosine.