Pneumothoraces are a common problem in the ER and the ICU. The traditional screening test for a pneumothorax in the hospital is the chest radiograph; however, chest radiographs are not very sensitive in the setting of trauma and in ventilated patients. A recent study of 225 trauma patients demonstrated that an AP chest x-ray had only 20.9% sensitivity for detecting a pneumothorax versus a CT scan of the chest. A chest CT scan is the gold standard for the diagnosis of a pneumothorax, but a CT scan is extremely expensive and exposes a patient to about 7 mSv radiation (the equivalent of 70 chest x-rays). Another modality that is gaining traction as the principal diagnostic modality to evaluate for post-traumatic pneumothoraces is a transthoracic ultrasound. Thoracic ultrasound look for the presence or absence of lung sliding, comet tail artifacts, A line, a lung point, and a “Seashore sign” or “Bar code sign” on M Mode sonography to determine whether a pneumothorax is present. A transthoracic ultrasound takes only a few minutes to perform and is performed as a part of the E-FAST exam right in the trauma bay of the ER. It costs nothing, is associated with no radiation exposure, and requires no transport of the patient.