This book enables the reader to gain a rapid understanding of GC/MS analysis through a basic knowledge of the fundamental principles, linking these with simple and practical applications in the field of industrial medicine and analysis of drugs. Additional information from other specialist fields is also provided with the aim of helping the analyst to understand their relevance to the interpretation of results. The book describes efficient methods of sample preparation and quality assurance and provides information on epidemiology and pharmacology, without which drug screening is impossible. This comprehensive overview is mainly written for the practical analyst in the clinical laboratory but it is equally suited for teaching purposes.