Major events often require on-site medical capability to treat minor illness and injury, stabilize higher-acuity patients, reduce unnecessary ambulance transport, and preserve EMS system capacity. A medical aid station should not be treated as a tent with supplies. Its mission, staffing, treatment capability, security posture, patient tracking, communications, sustainment, and relationship to the larger incident organization should be defined before the event begins. This checklist is intended to help Fire/EMS leaders and partner agencies build a medical aid station that is operationally useful, clinically appropriate, and integrated into the event plan.