Ultrasonography is an established modality in medical imaging and is evermore entering clinical practice. This chapter provides an introduction to the principles of clinical ultrasonography. It describes the use of airway ultrasonography for identification of the cricothyroid membrane, the trachea and for confirming correct tracheal intubation. Bedside ultrasonography by the anaesthetist has a much higher success rate than palpation for identifying the cricothyroid membrane, especially in patients with neck pathology. It should be applied before initiation of airway management and not be delayed until airway problems are apparent. The role of lung ultrasonography for identification of normal ventilation and pathology is described. Gastric ultrasonography for assessing the starvation status of a patient is described.