Twenty-one compartment syndromes of the thigh in seventeen patients were identified for retrospective review. Ten of the compartment syndromes were associated with an ipsilateral femoral fracture; five of these femoral fractures were open. In five patients, the syndrome followed femoral intramedullary stabilization. The remaining eleven syndromes followed blunt trauma to the thigh, prolonged compression by body weight, or vascular injury. The patients who were awake and alert at the time of the examination complained of intense pain in the thigh, and they had neuromuscular deficits. For the patients who could not cooperate with a subjective physical examination because they were under general anesthesia or because of associated injuries, the measurement of compartment pressure assumed a more important diagnostic role. All of the patients had tense swelling of the involved thigh. The predisposing risk factors for the development of compartment syndromes of the thigh, which are common in the multiply injured population, include: systemic hypotension, a history of external compression of the thigh, the use of military antishock trousers, coagulopathy, vascular injury, and trauma to the thigh, with or without a fracture of the femur. In approximately one-half of these patients, a crush syndrome developed, with myoglobinuria, renal failure, and collapse of multiple organ systems. Eight patients (47 per cent) died as a result of multiple injuries. Of the nine patients (ten compartment syndromes) who survived, infection developed at the site of the fasciotomy in six. Follow-up examination revealed marked morbidity, including sensory deficit and motor weakness of the lower extremity.(ABSTRACT TRUNCATED AT 250 WORDS)