The combination of the unique pathologic features of usual interstitial pneumonia (UIP) on biopsy, the progressive clinical course, and resistance to anti-inflammatory therapy constitutes the cardinal manifestations of what is termed idiopathic pulmonary fibrosis (IFP)/usual interstitial pneumonia, and it has led to recent suggestions that new therapies should be directed at regulating fibroblast functions rather than targeting the inflammatory response. The observation that "early" UIP looks like "late" UIP but there is less of it has been largely responsible for re-evaluation of the paradigm that IPF is the result of uncontrolled lung inflammation. This article highlights aspects of current thoughts on pathogenesis of IFP and expands on recent reviews.