The paper is aiming at a critical review of some important aspects of library cooperation in cataloging. It examines the developments of cooperation in cataloging in brief, attempts a detailed account of centralized and cooperative cataloging by bringing out the strengths and weaknesses of each, and reviews important cooperative projects in cataloging as they have been carried out on regional, national and international levels. Examination is made of such cooperative ventures as technical service centers, a variety of Library of Congress programs designed to ease the burden of cataloging for libraries, and the shared cataloging part of the National Program for Acquisition and Cataloging.