This paper prepared at the request of the South African Institute for Librarianship and Information Science develops a scientific definition for librarianship and guidelines for librarians based on that definition. An abridged version of the author's doctoral dissertation, the paper shows that a definition of librarianship is essential for the library profession and for any systematic investigation of library science. The requirements for a scientifically tenable definition are presented and current definitions are classified, tested, and rejected. A new definition of librarianship is formulated to cover all libraries and similar institutions irrespective of time or place. Guidelines for the library profession and for the study of librarianship are also given, and a list of topics to be included in a library science curriculum is provided. An extensive reference list and the author's vita are included. (ESR)