Physicians may encounter medical emergencies outside a hospital or clinical setting, such as on an airplane or at a sporting event. Physicians, particularly critical care physicians, should feel a call of duty to assist in a medical emergency and may do so without complete knowledge of existing laws for protection. The intent of this article is to encourage physicians to have a detailed awareness of Good Samaritan laws in the United States. The authors reviewed and summarized the Aviation Medical Assistance Act (AMAA) as well as the Good Samaritan laws and external defibrillator laws in 50 states and the District of Columbia. Physicians have an ethical duty to provide appropriate emergency care outside hospital or clinical settings and, therefore, should be aware of applicable protective laws. On airplanes, the AMAA provides protection to those physicians acting in Good Samaritan roles on airlines registered in the United States. On the ground, physicians should understand that statutes exist in all jurisdictions to protect Good Samaritans from liability in medical emergencies and in the use of defibrillators. Although there are common elements, each state has its own unique statutory language protecting physicians licensed in that state. All states except Kentucky have statutory language providing immunity to physicians licensed in any other state as well. Some states have interesting statutes relative to other aspects of medical emergency care. A physician entrusted to practice medicine by society and law should be willing to provide appropriate medical care wherever needed.