This paper describes some results of the DELTA Project ‘Educational Systems based on Multimedia Databases of Learning Material’. The project addressed the problem or courseware re-usability by developing a data base structure suitable for organising multimedia learning material in a given content domain. The proposed conceptual structure provides a characterisation or the material in terms of its physical and pedagogical features; so that both the author of courseware and the learner can formulate queries to the database in terms of the topic(s) they are interested in, the cultural background, the objectives, the degree of detail and other features of their educational needs. Of course, the exploitation of such a database also requires the development of customised applications, allowing users to perform a variety of activities: browsing for information, navigating freely or under the guidance or a supervisor, editing the material, authoring courseware, etc. A prototype or one such application, the browser, is then described. This is a software system allowing its user to query and navigate a DBLM (Data Base or Learning Material) on Earth Science. The feasibility or this approach is finally discussed on the basis of some preliminary experiments.