G M 1 ganglioside, administered to young C57/B16J mice with moderate (approx 85%) 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced striatal dopamine depletions, caused a dose-dependent increase in striatal dopamine levels. This effect was maximal between 7.0 and 30.0 mg/kg and was not apparent at higher and lower doses of G M 1 . G M 1 ganglioside treatment had no effect on striatal dopamine levels in mice with more extensive lesions of the dopamine system (i.e. approx 93% loss of striatal dopamine). The semisynthetic ganglioside derivative LIGA 20, administered orally, also increased striatal dopamine levels in moderately lesioned animals, albeit at lower doses than G M 1 . LIGA 20 administration also resulted in increased striatal dopamine levels in animals with more extensive dopamine lesions, where G M 1 had no effect. These results show that both G M 1 and its semisynthetic derivative LIGA 20 can partially restore striatal dopamine levels in MPTP-treated mice and that LIGA 20 is more potent and not subject to the same dose-limiting effects as G M 1 .