This document provides an overview of ultrasound applications in the intensive care unit and emergency department. It discusses using ultrasound at the bedside for lung imaging as an alternative to radiography. It describes the signs of pneumothorax, pulmonary edema, pulmonary embolism, and lung consolidation seen on ultrasound. The document also reviews using ultrasound to evaluate the inferior vena cava, heart, and pericardial space. Protocols for lung ultrasound and applications in critically ill patients are presented.