Pulmonary function abnormalities in Parkinson's disease (PD) might predispose patients to obstructive sleep apnea (OSA) and daytime sleepiness. Fifty-five idiopathic PD patients (mean age = 63.9) underwent three consecutive nights of in-laboratory polysomnography on their usual dopaminergic medications. Sleep apnea severity was compared to published, normative, population-based data from the Sleep Heart Health Study. Demographic and clinical data were compared in patients with and without OSA. The apnea-hyponea index (AHI) was stable across nights in PD patients, and was not different between PD patients and normative controls. Epworth Sleepiness Scale scores, Body Mass Index, and snoring did not correlate with AHI. Severity of OSA is stable across multiple nights in PD patients. Rates of OSA in PD are similar to those seen in the general population. Daytime sleepiness, snoring, and obesity may not be helpful in identifying OSA in PD.