The current practice of characterization and control of impurities in pharmaceuticals is reviewed with emphasis on issues specific to the generic industry. This review includes an overview of FDA, ICH, TGA, TPD and EMEA guidelines related to impurities in Drug Substance and Drug Products. This introduces the identification, characterization and qualification procedures for ANDAs and approaches to the establishment of acceptance criteria for both drug substance and drug product and significance of analytical methods in total process.