Proper mass gathering medical planning can help to mitigate the inherent risks and system-wide challenges that these events present. Mass gatherings put pressure on the EMS response system and other community resources, including hospitals, transportation, and law enforcement. Effective mass gathering medical planning prepares not only for historic patient presentation rates from similar events during normal operations but also must incorporate appropriate public health measures and anticipate escalating events that produce multiple casualty incidents. Consideration of an adequate pre-event timeline, available resources, relevant stakeholders and regulations, venue capabilities, environmental factors, and reliable communications are important in the planning stage. Successful medical plans are adapted to the specific event and can include mobile responder teams or various levels of treatment facilities. Despite the best-prepared medical plans, the potential of a multiple casualty incident is always present, and medical staff should be ready to convert into disaster operation response when necessary.