Abstract: OBJECTIVE: To assess deployed Gulf War (GW) veterans for prodromal Parkinson's Disease (PD) using the REM Sleep Behavioral Disorder (RBD) Screening Questionnaire (RBDSQ). METHODS: GW veterans ( n = 165) were assessed for nonmotor PD symptoms with the RBDSQ, Non-Motor Symptoms Scale, and Scales for Outcomes in Parkinson's Disease-Autonomic. Some veterans were also assessed with the University of Pennsylvania Smell Identification Test ( n = 120), neurological examinations ( n = 41), and 3T magnetic resonance imaging ( n = 16). RESULTS: Eighty percent of veterans with PD and 73% of veterans without PD had probable RBD (ie, RBDSQ ≥5). Exploratory analysis conducted for hypothesis-generating purposes revealed that RBDSQ scores were positively associated with GW deployment-related exposures and inversely associated with brainstem volume. CONCLUSIONS: These findings suggest that veterans with GWI and high levels of deployment-related exposures are at risk for prodromal PD, possibly through RBD as a mediator.