We compared the frequency of rhinorrhea between 34 Parkinson's disease (PD) subjects and 15 normal controls (NC) and explored relationships between rhinorrhea and clinical functions, and degree of nigrostriatal dopaminergic denervation using [ 11 C]dihydrotetrabenazine (DTBZ) brain positron emission tomography imaging. Sixty-eight percent (23 of 34) of PD subjects reported rhinorrhea of any cause compared with 27% (4 of 15) of NC (v 2 5 7.07, P 5 0.008). Rhinorrhea frequency remained higher in the PD group after excluding possible rhinitic etiologies: 35% (12 of 34) of PD versus 7% (1 of 15) of NC (v 2 5 4.38, P 5 0.04). There were no differences in demographics, nigrostriatal dopaminergic denervation, and clinical motor or nonmotor variables between PD subjects with and without rhinorrhea, except that more PD subjects with rhinorrhea complained of lightheadedness (52% vs. 9%, v 2 5 5.85, P 5 0.02). Rhinorrhea is a common nondopaminergic feature of PD, unrelated to olfactory or motor deficits. Further investigations are needed to determine if rhinorrhea correlates with sympathetic denervation or other autonomic symptoms in PD. V