This book demonstrates the recent advances in rapid on-site evaluation (ROSE) for differential diagnosis of interstitial lung disease (ILD). Interstitial lung disease is a group of diffuse parenchymal lung disorders affecting the interstitium, a part of the lung's anatomic structure, causing inflammation, scarring, or excess fluid. ILDs include interstitial pneumonia, idiopathic pulmonary fibrosis, nonspecific interstitial pneumonitis, cryptogenic organizing pneumonia and sarcoidosis, which are associated with various degrees of morbidity and mortality rates. ROSE has proven its value in diagnosis with routine transbronchial lung biopsy (TBLB) procedures, especially in difficult clinical cases. The first part of the book discusses the principals of performing ROSE procedures, reviews the basic concepts and summarizes the distribution and morphology of tracheal/ bronchial/ pulmonary cells. The second part covers specific interstitial disorders, including a number of difficult and rare cases, and features iCT images and cytological illustrations. Providing readers with valuable insights, the book is an important resource for practitioners involved in the care and treatment of patients with ILD. This book is part of the 4-volume collection ROSE in Diagnostic Interventional Pulmonology.