Authors reviewed and reported on articles and books about war-related illnesses published since 1863. Poorly understood war syndromes have been associated with armed conflicts since the Civil War. Although there are similarities of symptoms among these syndromes (each conflict resulted in a new name for its syndrome), no single recurring illness is apparent. Although veterans of each war were carefully scrutinized, research efforts to date have been unable to demonstrate causality, have been subject to reporting bias, and have lacked similar control populations. Unless our understanding of health and illness improves, we risk repeated occurrences of unexplained symptoms among veterans after each war.