Book excerpt: This book summarizes the branch tracing method for bronchoscopic diagnosis. Cytopathological and histopathological diagnoses are essential to making prognoses and selecting appropriate treatment for peripheral pulmonary lesions, notably lung cancer. In order to collect cell and tissue samples from peripheral pulmonary lesions for cytopathological and histopathological diagnoses, exfoliative cytodiagnosis and biopsy under bronchoscopy with endobronchial ultrasonography (EBUS) are currently used worldwide. Bronchial Branch Tracing highlights how to identify the bronchial branches that lead to peripheral pulmonary lesions and offers a valuable guide for all respiratory physicians, as well as surgeons, who frequently perform bronchoscopies, helping them understand the method and improve their technique.