We encountered 2 cases of microscopic polyangitis (MPA) with preceding interstitial pneumonia. The patients were elderly men, and radiological findings showed a UIP pattern in both cases. Furthermore, ANCA-associated vasculitis had been suspected since the first admission in case 1, because MPO-ANCA tests were positive, and the surgical lung biopsy revealed vasculitis in a honeycomb lesion. A diagnosis of idiopathic pulmonary fibrosis was made in case 2 because no findings of vasculitis were pathologically confirmed, and MPO-ANCA was not examined. Both patients were followed up without any treatment, but steroid therapy with immunosuppressants was initiated after a diagnosis of MPA was made from a renal failure complication. Remission continued in case 1, but patient 2 died due to a pulmonary hemorrhage complication, despite some temporary improvements. An autopsy revealed massive alveolar hemorrhage and neutrophil infiltration in the alveolar walls that suggested pulmonary capillaritis, in spite of the absence of pathological evidence, which was not detected in the honeycomb lesions. These 2 cases indicate that MPO-ANCA should be examined in the follow-up of chronic interstitial pneumonia. Furthermore, it should be assumed that the size of involved blood vessels, their distribution and the timing of occurrence may be different in individual case of ANCA-associated interstitial pneumonia.