Idiopathic pulmonary fibrosis (IPF) is a progressive disease with a dismal prognosis for which, until recently, there were no effective treatments. Pirfenidone (5-methyl-1-phenylpyridin-2[1H]-one) is a novel antifibrotic agent that has been demonstrated to slow disease progression in patients with IPF. In vitro and in vivo animal models of pulmonary fibrosis have shown that pirfenidone exerts its effect by reducing inflammatory cytokines such as TNF-α, by downregulating the transcription of key profibrotic growth factors including TGF-ß, and through reductions in lipid peroxidation and oxidative stress. In three of four multicenter, randomized, placebo-controlled trials in patients with IPF, pirfenidone has been shown to slow disease progression as measured by decline in forced vital capacity over 36-72 weeks. In general, in these clinical trials, pirfenidone was safe and well tolerated. Reported adverse effects include nausea, anorexia and photosensitivity dermatitis. A number of questions remain concerning the long-term efficacy and safety of pirfenidone and whether slowing of lung function decline will translate into improved survival for patients with IPF. These questions notwithstanding, pirfenidone represents an important development in the treatment of IPF and is a much needed addition to the previously inadequate therapeutic armamentarium for this devastating disease.