In this pilot study, we performed an oral yohimbine challenge in 6 patients with Parkinson's disease (PD) and anxiety or depression, 2 parkinsonian patients without psychiatric illness, and 2 healthy control subjects to determine whether patients with Parkinson's disease and anxiety respond to this adrenergic agent in the same way patients with idiopathic anxiety disorders respond. Given the atypical nature of depression in Parkinson's disease (characterized by prominent anxiety), we also wanted to see if patients with Parkinson's disease and depression (but no history of anxiety) are susceptible to yohimbine-induced panic. Parkinsonian patients with anxiety developed panic attacks at frequencies comparable to primary psychiatric patients with panic disorder. The one patient with PD and a history of major depression alone developed a panic attack. Regardless of their history of anxiety or depression, parkinsonian patients demonstrated a vulnerability to yohimbine-induced somatic symptoms.