A variety of conditions can be associated with localized areas of fibrosis within the lungs. The most frequent causes of these lesions are healed infections. Old healed tuberculosis, fungal infections, and necrotizing pneumonias or abscesses can result in scar formation. Calcification and even ossification are common in focal scars, especially healed foci of necrotizing granulomatous inflammation. Vascular diseases may result in localized scars, particularly healed infarcts secondary to thromboemboli. Traumatic injuries such as gunshot wounds, shrapnel, or fractured ribs may also result in focal scars within the lung. It is important to know if a biopsy of fibrotic lung tissue represents a focal lesion as opposed to diffuse interstitial fibrosis because of the very significant differences in clinical implication.