It was originally intended that this paper should present a description of the traditional structure of an information service and an indication of how that structure changes as a result of introducing external information services. Although during the writing of the paper this intention has been kept constantly in mind, the author has found it impossible not to stray into describing changes of function and the resulting changes in attitudes on the part of information worker and user. This is for two reasons. Firstly, the resultant changes in function and changes in attitude are still very much in a formative stage, and until they are reasonably crystallized it would be foolish to venture too far in discussing possible changes in structure. Secondly, formal organizational structures are becoming outmoded in modern management practice; informality and the highest degree of flexibility are the latter's key notes.