Nine patients with diffuse intrapulmonary hemorrhage and glomerulonephritis not due to anti-glomerular basement membrane (anti-GBM) antibody are described and similar previously reported cases are reviewed. Eight patients were seen during a four-year interval and represented 47 percent of the cases of pulmonary hemorrhage and glomerulonephritis seen during this period. Diagnoses included systemic vasculitis of unspecified type in two patients with seropositive rheumatoid arthritis, idiopathic crescentic glomerulonephritis with negative immunofluorescence in two, Wegener's granulomatosis in two, and polyarteritis nodosa, Henoch-Schönlein purpura, and mixed connective tissue disease in one each. Differentiation from anti-GBM antibody-mediated pulmonary hemorrhage and glomerulonephritis by clinical evaluation alone was frequently difficult, emphasizing the importance of both immunopathologic studies and evaluation of serum for anti-GBM antibody in all patients with pulmonary hemorrhage and glomerulonephritis. In eight of nine patients, significant episodes of pulmonary hemorrhage improved markedly within 24 to 72 hours following initiation of high-dose corticosteroid therapy. In contrast, renal function did not improve in the majority of patients.