Coffee drinking and cigarette smoking have been linked to a reduced risk of Parkinson disease (PD), but recent clinical trials indicate that neither caffeine nor nicotine can relieve the symptoms of this condition. In the Café-PD trial, 121 patients with PD were randomly assigned to receive 200 mg caffeine or placebo capsules twice daily for up to 18 months. The caffeine treatment did not significantly improve the motor manifestations of PD, as assessed on the United PD Rating Scale (UPDRS). In the other trial, which involved 40 patients with PD, half of the participants received transdermal nicotine therapy; the treatment produced no significant improvements in UPDRS scores over a 39-week period. These findings indicate that the inverse relationship between caffeine and nicotine intake and PD risk is unlikely to be attributable to symptomatic effects.