All of the GWS patients will be registered in the Gulf War Veterans Registry. To avoid referral bias favoring the presence of IFL during sleep and sleep disordered breathing, we will enroll GWS patients by contacting them from the Registry and inviting them to participate. Gulf War veteran controls will be recruited in the same way and by advertisement. Prospective study participants will be screened on several self-report instruments to determine eligibility and assignment to the GWS group or to the Gulf War veteran control group.