Upon return from 1991 Gulf War (GW), many veterans began suffering from a wide range of health symptoms of unknown etiology. These symptoms encompass 6 major domains including cognitive and sleep, pain, neurological and cognitive, respiratory, gastrointestinal, and skin manifestations, which have come to be categorized as Gulf War Veterans’ illnesses (GWVI). GWVI is a multisystem disease estimated to affect 25% of GW Era veterans. Neuroinflammation and neurodegeneration have been postulated to underlie GWVI symptoms. A need in the field is to better define GWVI, and distinguish symptom clusters within GWVI, in order to develop targeted treatments. Our central hypothesis is that a comprehensive neurosensory testing protocol can be applied to the study of GWVI to distinguish GWVI case groups from controls and to identify sub-groups within GWVI. This protocol consists of applying quantitative sensory testing (QST) strategies to evaluate the integrity of sensory processing mechanisms (Aim 1), examining trigeminal neural circuit responses to light using functional magnetic resonance imaging (fMRI) (Aim 2), and examining neuro- inflammatory signatures in blood (Aim 3) in individuals with GWVI and appropriate controls. The combined results of these three aims will allow us to examine which neurosensory metrics, in isolation or combination, are most useful in predicting GWVI phenotypes. Along with forwarding our understanding of GWVI pathophysiology, these data can be used to develop tests that can be used in the clinical arena to sub-group individuals based on underlying mechanisms, an important first step to developing targeted therapies.