Four patients who developed symptoms of Goodpasture’s syndrome during the winter 1971–1972 from a geographic area of about a 25mile radius have been studied. There was an epidemiological association between these cases and a concurrent outbreak of influenza A2; however, corroborative virologic or serologic evidence could not be obtained. All patients had typical clinical manifestations of severe pulmonary and renal disease. Immunofluorescence studies revealed linear deposits of IgG in all glomeruli studied. C3 was present in three of the four in a granular pattern. Properdin was present in one and C4 in each of the three patients stud