This book is an overview of the hazards of firefighting, the health risks of exposure to combustion products that characterize firefighting, the science behind interpreting these risks for purposes of identifying diseases as work-related, and the legal and policy implications of adopting legislated “presumption” for purposes of compensation. The emphasis of the book will be on the risk of cancer, cardiovascular disease, traumatic hazards, and disabling psychosocial adjustment following major incidents. Several new studies have appeared recently, including the largest study of firefighters ever done, by the National Institute of Occupational Health and Safety (NIOSH). They evidence supports the conclusion that firefighters face significant occupational health risks in addition to the obviously severe safety hazards.