The Hamman-Rich syndrome is defined as an acute pulmonary disease of unclear aetiology that takes a rapid and prognostically unfavourable, usually fatal course. We report on three patients admitted to the intensive-care ward during a period of 6 months in a state of mandatory artificial respiration, each patient dying within 3 weeks after admission. Basing on clinical and histological criteria these patients were diagnosed as suffering from Hamman-Rich syndrome. At the time of the clinically identifiable onset of the disease all the patients had fever (> 39 X), leucocytosis (> 20 x 10(3)/microliters) and dyspnoea. These signs and symptoms were at first, in conjunction with the radiological identification of diffuse pulmonary infiltrations, misdiagnosed as pneumonia. The patients had to be artificially respirated after a short time because of the foundroyant course of the disease. Despite optimised respiratory parameters it was already initially apparent that there was a severe disturbance of the gas exchange function (paO2/FiO2 < 150) and high respiratory pressures (> 40 mmHg). Polymorphonuclear neutrophilics dominated in the bronchoalveolar lavage. Lung biopsy showed marked fibrosing that was a decisive factor in diagnosing. An infectious agent as triggering cause of the disease could not be identified in any of the patients. Treatment was effected with antibiotics, steroids and cyclophosphamide. The patients died after 14, 17 and 21 days, respectively, from intractable respiratory insufficiency with increasing loss of compliance of the lungs (compliance of lungs and thorax < 20 ml/mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)