This book discusses the role of genetic polymorphism in susceptibility to cancers. The book explores the understanding of differences between the genetic polymorphisms and mutations.It reviews the mechanisms underlying the effect of polymorphism in genes encoding proteins that play an essential role in metabolism, signal transduction, cell cycle, and DNA repair mechanisms. Further, it investigates various techniques that are used for analyzing the genetic polymorphisms. The book contains many chapters which summarize the importance of genetic information obtained from polymorphism-based pharmaco-genetic tests to predict better drug response and life-threatening adverse reactions to chemotherapeutic agents, help in understanding of the impact of SNPs on gene function, and gives overview of the different SNP databases for examination. This book, therefore, serves as an essential guidebook for independent researchers as well as institutions working in this specialised field.