In response to the health concerns of Gulf War veterans, the Department of Defense instituted the Comprehensive Clinical Evaluation Program (CCEP). Although not designed as a research study, the CCEP provided valuable clinical data. An analysis was conducted of CCEP findings from systematic and comprehensive examinations of 20,000 U.S. Gulf War veterans. Among 20,000 participants, the types of primary and secondary diagnoses varied widely. Also, among veterans with an ICD-9-CM diagnosis of "symptoms, signs, and ill-defined conditions," no single subcategory of illness predominated, and no characteristic physical sign or laboratory abnormality was identified. In-total, there were 74 (0.4%) cases of connective tissue disease; 52 (0.3%) noncutaneous malignancies; 42 (0.2%) peripheral neuropathies; 14 (0.07%) cases of interstitial pulmonary fibrosis; 12 (0.06%) cases of renal insufficiency; and no new cases of viscerotropic leishmaniasis. No clinical indication of a new or unique illness was identified in this self-referred population, and the types of physiologic disease that could result from postulated hazardous wartime exposures were uncommon.