Because many occupationally exposed workers are disabled by medically unexplained symptoms, the authors set out to develop etiologically, prognostically, and therapeutically distinct diagnostic categories for these patients. Rigorous diagnostic criteria were applied to a sample of 21 patients with disproportionate disability: three patients had typical posttraumatic stress disorders (PTSD), seven had atypical PTSD, and the remainder suffered somatoform disorders. Recognition of PTSD is important because, unlike somatoform disorders, PTSD often responds to appropriate treatment. Some of the factors that may lead to PTSD are discussed, based on the case series. Using case examples, the authors discuss the diagnostic criteria for typical and atypical PTSD; differentiate these from somatoform disorders; and discuss the implications of the study for prevention of PTSD and for case management.