The efficacy and technical aspects of endobronchial ultrasound (EBUS) are reviewed because this technology promises to revolutionise bronchoscopy. EBUS extends the endoscopist's view beyond the mucosal surface of the large airways to peri-bronchial structures and peripheral lung lesions. Guided biopsies and real-time transbronchial needle aspirations (TBNA) have been shown to increase the diagnostic yield over conventional bronchoscopic techniques. The technology is available in two forms: radial EBUS probes and linear EBUS-TBNA bronchoscopes. Radial EBUS utilizes higher frequencies and the transducer is inserted via a standard flexible bronchoscope. The higher ultrasound frequencies improve image resolution to <1mm. Radial EBUS is used to assess airway walls, guide TBNA (diagnostic yield: 72-86%) and diagnose peripheral lung lesions (diagnostic yield: 61-80%). Linear EBUS-TBNA transducers are built into dedicated bronchoscopes to produce sector view images and permit real-time TBNA. The pooled sensitivity of real-time EBUS-TBNA in lung cancer is 90% but the false negative rate is 20%. Therefore, EBUS-TBNA is a viable alternative to cervical mediastinoscopy in the diagnosis and staging of mediastinal lymphadenopathy. However, negative results need either further confirmatory testing or adequate clinical follow-up. Complications are rare with either EBUS modality and are usually related to the underlying biopsy procedure rather than the use of ultrasound. Procedure duration is short enough to be incorporated into an outpatient setting and can performed under moderate sedation. Clear training standards are emerging to facilitate credentialing as EBUS is rapidly evolving to become a part of standard diagnostic bronchoscopy.