Microscopic polyangiitis (MPA) is one of the vasculitides that is included in the pulmonary renal syndromes. Pathologically, MPA has been defined as necrotizing vasculitis with few or no immune deposits, primarily affecting small vessels including arterioles, venules, or capillaries. Pulmonary interstitial fibrosis (PIF) as an accompanying manifestation in MPA has not been widely appreciated. In the present study, we report six cases of MPA at our institution with radiographic evidence of PIF that was apparent before any treatment was administered. All had biopsy evidence of renal disease that was consistent with MPA as well as positive serum perinuclear antineutrophilic cytoplasmic antibody titers. Hemoptysis was observed in approximately one half of the patients. As determined by CT of the chest, PIF was detected in all of the patients and was often present years before a diagnosis of MPA was made. We conclude that PIF may occur as a pulmonary manifestation of MPA. Further appreciation of this finding may lead to more data with respect to the incidence of PIF in MPA, and to a better understanding of the mechanisms that are involved in the development of this finding.