We report here 4 cases of rapidly progressive glomerulonephritis (RPGN) which developed during the management of idiopathic pulmonary fibrosis. In each patient, pulmonary disease preceded the onset of nephritis by 1 to 6 years. All patients had a high titer of serum autoantibodies against myeloperoxidase (MPO-ANCA) when the diagnosis of RPGN was made. Although the association of pulmonary fibrosis with ANCA-related glomerulonephritis has been occasionally described in the past literature, the sequence of pulmonary and renal injury has not been well defined. The present report demonstrates that idiopathic pulmonary fibrosis exists as a preceding condition in some patients with MPO-ANCA-related nephritis.