PURPOSE OF REVIEW: This review examines the evidence for the causality and pathogenesis of lung cancer associated with interstitial lung disease. RECENT FINDINGS: Although cigarette smoking is the leading cause of lung cancer, several other conditions either predispose to lung cancer or increase the risk of lung cancer in smokers. The evidence supports an increased risk of lung cancer due to specific fibrotic and inflammatory lung diseases (termed interstitial lung diseases), including idiopathic pulmonary fibrosis, systemic sclerosis, and certain pneumoconioses. The potential pathogenetic mechanisms indicate that recurrent injury and inflammation result in genetic alterations that predispose to lung cancer. SUMMARY: Idiopathic pulmonary fibrosis, systemic sclerosis, and certain pneumoconioses are associated with an independent increased risk of lung cancer; however, a unifying pathogenetic mechanism to explain the causality of this association has not been described. In addition, the inconsistently reported lung cancer frequencies call attention to the need for prospective studies of good quality.