Using simple and standardized semiology, the lung appears accessible to ultrasound, despite previous opinions otherwise. Lung ultrasound allows the intensivist to quickly answer to a majority of critical situations. Not only pleural effusion but also pneumothorax, alveolar consolidation, and interstitial syndrome will have accurate ultrasound equivalents, the recognition of which practically guides management. Combined with venous, cardiac, and abdominal examination, ultrasound investigation of this vital organ provides a transparent overview of the critically ill, a kind of stethoscope for a visual medicine. It is believed that by using this tool, the intensivist may more confidently manage acute dyspnea and make emergency therapeutic decisions based on reproducible data. Further benefits include reduced requirements for computed tomographic scans, therefore decreasing delay, irradiation, cost, and above all, discomfort to the patient. Thus, ultrasound of the lung can also be added to the classic armamentarium as a clinical tool for emergency use.