The aim of this thesis is to describe and compare the cataloguing rules for sound recordings: the rules used by a specialised archive and common libraries respectively. We will put the rules in relation to purposes (the objectives of a bibliographic system) and principles (directives that guide the construction of a bibliographic language). The first question to be answered is in which way the set of rules used by a specialised archive differ from the one used by common libraries. The second question examines if and how the differences can be derived from purposes and principles. The sets of rules studied are KRS (chapter 6) and the Swedish version of the IASA Cataloguing Rules (1999), worked out by the National Archive of Sound and Moving Images (SLBA). The rules are compared, and the differences described and discussed in relation to the purposes and principles in Elaine Svenonius’ The Intellectual foundation of Information Organization (2000). The study shows that the rules answer to the principles and purposes, but indicates some differences. The SLBA version answers better to the principle of user convenience and the subprinciple of common usage: the user is in focus in decisions regarding new descriptions. KRS (chapter 6) answers better to the principle of representation and the subprinciple of accuracy: the description should be exact. The SLBA catalogue could be described as a “full-featured bibliographic system”; it addresses the user’s needs and helps to spread knowledge in the science community. / Uppsatsnivå: D