Apart from its usefulness in general anesthesia, Nitrous oxide has definite advantages in small outpatient procedures in dentistry and surgical practice. Nitrous oxide with oxygen gives good analgesia without significantly affecting the level of consciousness and vital parameters. It is especially preferred in pediatric dental procedures as it does not involve painful injections. With all its advantages, there is a limitation for its use in clinics and operation theaters that do not have proper air scavenging systems. The doctors, dentists, nurses, technicians and other support staff working in such environment may get chronic exposure of Nitrous oxide which may adversely affect their health. This book consists of reviews from selected publications on the adverse events and toxicities of chronic Nitrous oxide exposure and results of preclinical research conducted in Wistar albino rats subjected to chronic Nitrous oxide exposure with specific reference to neurological, haematological and histological effects.