Medical surge forms the cornerstone of preparedness planning efforts for major medical incidents. Surge capacity encompasses multidimensional aspects such as potential patient beds; available space in which patients may be triaged, managed, vaccinated, decontaminated, or simply located; available care personnel of all types; necessary medications, supplies, and equipment; and even the legal capacity to deliver health care under situations that exceed authorized capacity. Further, close collaboration between public health and health care facilities is very important to effective disaster response. In the aftermath of the September 11 terrorist attacks and the dissemination of anthrax in 2001, the ability of the US health care system to provide an effective and coordinated response to mass casualty or complex incidents came under intense scrutiny. More recently, the devastation caused by Hurricane Katrina and the mass disruption of public health and medical services along the Gulf Coast spotlighted the need for cohesive strategies that focus on management systems for major public health and medical response. In this article, we explore hospital surge capacity planning. Specifically, we will discuss issues related to surge patterns, the interplay of care personnel and staff, facilities, equipment and supplies, and incident management system. Approaches used in balancing daily operational efficiency versus maintaining an appropriate surge capacity will be discussed, and the importance of international collaboration is highlighted. Further, OR methodologies, including simulation, optimization, stochastic processes and systems dynamics models used in medical surge analysis will be briefly reviewed.