The study design of the pilot study is case-controlled. A projected 120 male and female GW veterans who were deployed to the war zone and 38 male and female military personnel activated during the Gulf War will participate. Olfactory measures include olfactory identification, and odor intensity and pleasantness judgments, which have been revealed by factor analysis to reflect distinct olfactory components. Odors are presented using the University of Pennsylvania Smell Identification Test. A brief neurocognitive battery including standardized, age-normed measures of functions sensitive to neurotoxic exposure (i.e., attention, fine motor skills, executive functioning, and memory) are also administered. Psychopathology and self-reported health measures are also administered as part of the larger "Follow-up" study.