Linear endobronchial ultrasound (EBUS), also known as convex endobronchial ultrasound (CP-EBUS), is a flexible bronchoscope with a linear ultrasound probe at the tip. It enables EBUS-guided transbronchial needle aspiration (EBUS-TBNA) of mediastinal and hilar structures in real time under ultrasound guidance. This minimally invasive procedure is an established diagnostic tool that allows bronchoscopists to see beyond the airways while simultaneously performing diagnostics. Clinical applications of EBUS-TBNA include (a) lymph node staging in patients with lung cancer, (b) diagnosis of intrapulmonary tumors, (c) diagnosis of unknown hilar and/or mediastinal lymphadenopathy, and (d) diagnosis of mediastinal tumors. EBUS-TBNA has been shown to have a high diagnostic yield in the diagnosis and staging of lung cancer. New developments such as EBUS-guided forceps or cryobiopsy have further improved the diagnostic yield in situations such as lymphoproliferative diseases. EBUS-TBNA has almost completely replaced the more invasive procedure of mediastinoscopy and is now considered the primary diagnostic tool in the clinical applications described in this chapter.