Fast cyclic voltammetry at a carbon fibre microelectrode was used to measure dopamine release following electrical or chemical stimulation in rat brain slices incorporating either the ventral tegmental area or the core region of the nucleus accumbens. Electrical or chemical stimulation gave clear voltammetric signals which corresponded to dopamine; less dopamine was released in the ventral tegmental area than in the nucleus accumbens. In contrast to the nucleus accumbens, electrically stimulated dopamine release in the ventral tegmental area was not sensitive to tetrodotoxin, was not modified by the presence of dopamine uptake inhibitors, or agonist or blockers acting at dopamine D2 autoreceptors.