Expression of a cloned dopamine transporter complementary DNA in COS cells allows these primate kidney cells to accumulate the parkinsonism-inducing neurotoxin metabolite MPP+ (1-methyl-4-phenylpyridinium) avidly, and MPP+ toxicity results. By documenting that the dopamine transporter can confer MPP+ sensitivity to nonneural cells, these results highlight the key role that this transporter could play in mechanisms underlying parkinsonism.