A remarkable convergence of epidemiologic and laboratory data has raised the possibility that caffeine reduces the risk of developing Parkinson's disease (PD) by preventing the degeneration of nigrostriatal dopaminergic neurons. The authors review the evidence that caffeine and more specific antagonists of the adenosine A2A receptor protect dopaminergic neurons in several toxin models of PD. Other studies demonstrating protection by A2A receptor inactivation in animal models of stroke, Huntington's disease, and Alzheimer's disease suggest a more global role of A2A receptors in neuronal injury and degeneration. Although the cellular and molecular mechanisms by which A2A receptors contribute to neuronal death are not yet established, several intriguing possibilities have emerged. Now with preliminary clinical data substantiating the antiparkinsonian symptomatic benefit of A2A receptor blockade, the prospects for a complementary neuroprotective benefit have enhanced the therapeutic potential of A2A antagonists in PD.