Due to rapidly growth of centralized cooperative bibliographic services and resource sharing. it becomes apparent that a standard system is needed. AACR2R and MARC 21 is such standard system, where in AACR2R use in the construction of catalogues and the MARC 21 facilitate the exchange of bibliographic and related information. MACR 21 support the revised rules of AACR2R integrating resources both in print (loose-leaves) and electronic format (updating databases and web sites). This new manual aims to maintain the tradition established by AACR2 and MARC 21 and seeks to fulfill the same aims that is to provide a clear and comprehensively overview of modern cataloging theory, policy and practice and to provide a depth description of various fields of AACR2R into MARC 21. To facilitate reading and understanding the book is presented in 2 parts Part-I Description and Part-II Choice of Access points). This volume is intended as a blueprint of good cataloging practice. Thus this book is a must for librarians and students of library science. It has been tried to provide the guideline to user between AACR2 and MARC21 through this book .