The Project of the retrospective conversion of the Catalogue, meaning the transformation of the card and printed catalogues of the Library, so called historical catalogue, into an electronic database. Namely, an online Catalogue, accessible through Internet for a large group of users, in the country and abroad, is one of the major priority in the Work and Activity of the National Library of Serbia, for the next period. The draft of the Project and the explanation of the main reasons of the initialization of this important Project is given. Beside that, like in any other projects, the goals of the project are explained, as well as, the expected results for each separate phases in the realization of the Project. In the supplements, the details of different phases of the realization of the Project -Retrospective Conversion are described. The elementary sources, from which the conversion and the configuration the database will be performed, are mentioned. A layout of the procedure of the retrospective conversion is given in addition.