Introduction: According to the International Evidence-Based Recommendations for Point-of-Care Lung Ultrasound published in 2012, the sonographic technique for evaluating a patient for a pneumothorax (PTX) “consists of exploration of the least gravitationally dependent areas progressing more laterally” in the supine patient. However, there is a wide variety of scanning protocols in the literature with varying accuracy and complexity. We sought to derive an efficient and accurate scanning protocol for diagnosing pneumothorax using point of care ultrasound in trauma. Methods: We performed a retrospective chart review of a tertiary care trauma registry from Nov 2006 to Aug 2016. We included patients with a PTX diagnosed on computed tomography (CT). Patients were excluded if they did not have an identifiable PTX on the CT scan or if they underwent a tube thoracostomy prior to the CT scan. Penetrating and blunt trauma were eligible. Data were extracted with a standardized data collection tool and 20% of charts reviewed by two reviewers. Pre defined zones were used to map area of PTXs on CT. Sensitivity, specificity and 95% CI are reported for presence of PTXs in each individual or combination of lung zones as identified on CT scan. Results: Data were collection yielded 170 traumatic PTX on chest CT with an average age of 44.2 and 77.8% male. The kappa for data extraction was 0.88. 19.4% of patients had bilateral PTX leading to a total sample size of 203. The average ISS score was 20.7 and 93% of patients survived to discharge. The length of ICU stay and hospital stay was 3.7 and 11.2 days respectively. The most accurate and efficient protocol would involve scanning the inferior border of the clavicle at the para-sternal border and again at the mid-clavicular line down to the cardiac (left hemithorax) and liver lung points (right hemithorax). The sensitivity of this scanning area in the detection of PTXs was 91.6% (95% CI 86.9-95%,). Limiting the area to the most anterior point of the chest wall increased the risk of missing a PTX (Sensitivity 89.7% (95%CI 84.6-93.5)). Conclusion: We have derived an evidence-based standardized accurate and efficient scanning protocol to rule out a pneumothorax on point of care ultrasound.