The presence of hazardous materials or toxic chemicals at an incident location or other emergency situation adds a new dimension of risk to those handling and treating casualties. The fundamental difference between a hazardous materials incident and other emergencies is the potential for acute risk from contamination to both patient and responder. In some cases, traditional practices must be altered to avoid compounding a critical situation. Emergency medical services (EMS) must protect their personnel on site and en route to the hospital, and other people within the hospital, while providing the best care for the chemically contaminated patient. This guide is intended to help emergency medical services plan for incidents that involve hazardous chemicals and improve their ability to respond to these incidents. To ensure appropriate and timely patient care, as well as optimal response protection, emergency personnel must understand decontamination procedures and personal protective equipment, neither of which are routinely covered in the course of their professional training. They should also be aware of community resources that could be called upon to assist with an emergency response. Current training curricula for emergency room physicians and nurses and emergency medical technicians (EMTs) often do not adequately prepare these professionals to manage the contaminated individual or to decontaminate patients exposed to toxic substances. Accurate, specific, and concise guidance is needed to describe appropriate procedures to be followed by emergency medical personnel to safely care for a patient(s), as well as to protect responders, equipment, hospital personnel, and others from risk of secondary exposure. In response to this need, the Agency for Toxic Substances and Disease Registry (ATSDR) contracted for the production of a three-volume series entitled Managing Hazardous Materials Incidents: I. Emergency Medical Services: A Planning Guide for the Management of Contaminated Patients; II. Hospital Emergency Departments: A Planning Guide for the Management of Contaminated Patients; and III. Medical Management Guidelines for Acute Chemical Exposures. The second document is designed for use by emergency department personnel to minimize their risks of exposure within the emergency department, and to provide for the safe and effective treatment of chemically contaminated patients. This volume, written for emergency response personnel, is designed to familiarize readers with the terminology, concepts, and key operational considerations that affect the proper management of incidents of chemical contamination. It is designed not only to present uniform guidance for the emergency care of chemically contaminated patients, but also to provide basic information necessary to comprehensive planning and implementation of EMS strategies. It is intended to illustrate the characteristics of hazardous materials (hazmat) incidents that compel emergency response personnel to modify their preparations and response procedures. Not all hospitals and community emergency response systems are prepared to respond to a hazardous chemical incident to the same degree. This document may be used to assess the capabilities of EMS with respect to potential community hazards and to develop response plans using national and community-specific resources. Employee safety and training are also key factors in effective management of medical emergencies. This document is intended to provide source material for developing local training and safety protocols.