The paper summarizes the clinical course, histopathological examinations and immunohistological examinations of 4 personal cases [2 males aged 20 and 26 years, 2 females aged 65 and 18 years] of Goodpasture's pulmorenal syndrome. 2. The characteristic histopathological findings included pulmonary haemorrhage with a focal acute alveolitis and renal lesions that were classed as acute or subacute glomerulonephritis with the finding of scarce multinucleated cells. Such cells are regarded as being of diagnostic value and they are thought to indicate interaction of antibodies with the basement membranes. 3. Immunohistologically, all the cases showed a linear fluorescence following the basement membrane of the interalveolar septa. In 3 of the cases there was linear fluorescence in the glomerular capillary walls. In one case [observation No. 2] who had been hypertensive before death and had had necrotizing arteriitis at postmortem, there was fluorescence of granular type in the kidney believed to indicate the participation of immune complexes in the development of the pathological condition.