The development of the library catalog in book form and its abandonment in favor of the card catalog are briefly traced. The advantages and disadvantages of both types of catalogs are enumerated, and several solutions which tried to combine the best features of both are discussed. The present trend back to the book catalog, made possible by recent advances in computer technology, is analyzed, advantages and disadvantages are compared, current examples are illustrated, and finally the computerized catalog is weighed against both the book and card catalog as to main features and practicality.