The pathogenesis of idiopathic pulmonary fibrosis (IPF) is debatable. Looking for an insult to lung parenchyma that generates the pathogenesis of the disease is challenging. Pepsin is a proteolytic enzyme present in the gastric juice. Microaspirations of gastric content were described as a potential factor for injury in many chronic lung disorders. Bronchoalveolar lavage (BAL) is a routine investigation technique in interstitial lung diseases. The presence of pepsin in the BAL fluid recovered from patients with IPF may indicate a possible role for gastric microaspirations in the pathogenesis of the disease.