Chest diagnostic imaging is essential when dealing with a critically ill patient. At present, direct visualization of the lung parenchyma is performed with a chest x-ray and computed tomography with the patient in the supine position. The relative ease of bedside ultrasound examination and the availability of user-friendly, inexpensive, portable equipment have made chest ultrasonography an interesting and alternative method in various situations, because it offers accurate information that is of therapeutic and diagnostic relevance. We describe equipment and examination technique, normal findings, and chest ultrasonography signs detected in some pathological situations, such as pneumothorax, consolidations, pleural effusions, ARDS, and pulmonary edema.