Like GMP, GLP also originated in the United States of America. US FDA had observed in some cases that studies submitted in support of safety of regulated products had not been conducted in acceptable manner. In view of this, GLP guidelines were incorporated under the Code of Federal Regulations (21CFR 58) in late seventies. Based on these guidelines a group of countries known as Organization for Economic Cooperation and Development (OECD) developed GLP in early eighties. In India, GLP were incorporated under the Drugs and Cosmetics Rules as Schedule L1 in 2008 to be effective after two years. The former GLPs have been revised a couple of times. The first edition of this book was published in 2000 when no national GLP guidelines were available and discussion was mainly based on US FDA GLP. In view of the changes and appearance of GLP under the Drugs and Cosmetics Rules, third edition of the book has been published. Besides Indian GLP, US FDA GLP and principles of OECD GLP, associated topics like inspection, sampling, statistical quality control (SQC), analytical method validation, laboratory safety, NABL accreditation, GLP certification under OECD GLP Program have been included in the book to make it useful to the pharmaceutical industry and pharmacy educational institutions.