Amphetamine- and L-DOPA-induced changes in extracellular levels of striatal dopamine (DA) were monitored during rotational behaviour in rats with a unilateral 6-hydroxydopamine (6-OHDA) lesion of the nigrostriatal DA pathway. In vivo DA release measurements were obtained using intracerebral dialysis combined with high-performance liquid chromatography with electrochemical detection (HPLC-ED). In unilaterally denervated rats no DA was detected in dialysates collected from the striatum ipsilateral to the lesion while the contralateral side showed a compensatory increase in basal DA levels when compared to non-lesioned controls. Amphetamine (0.5-5.0 mg/kg s.c.) caused a dose-dependent release of DA in the striatum of normal rats and in the intact striatum of DA denervated rats but did not significantly release DA in the lesioned striatum. In response to amphetamine (0.5-5.0 mg/kg s.c.) lesioned animals showed dose-related ipsilateral rotational behaviour which in general correlated well with the time-course change in, and the total amount of, DA release in striatum contralateral to the lesion. In contrast to amphetamine, in lesioned rats, the DA precursor L-DOPA (20 mg/kg s.c.) induced readily detectable amounts of DA in dialysates collected from the DA denervated striatum. The L-DOPA-induced appearance of DA, which approached basal DA levels seen on the intact side, was concomitant with contralateral rotational behaviour. However, the time-course change in DA levels did not closely correlate with the apparently two-peak pattern of contralateral rotation induced by L-DOPA.