This report presents case studies of the role of school libraries and their transformation into school media centers in elementary and secondary schools in Serbia, Croatia, and Hungary. It is noted that the school media center is not conceived of as a simple mechanism for storing books and audiovisual aids, but as an active center for self-directed learning and innovative student-teacher relations. The studies were submitted in response to an invitation from the Unesco-supported Programme of Cooperation in Research and Development for Educational Innovation in South and South-East Europe. The Serbian study focuses on the transformation of school libraries in four primary schools. The study from Croatia describes the factors that prompted the establishment of resource centers and the standards established in this field. The library resource centers of two secondary schools, one for civil engineering and architecture and the other for medical workers, are described in detail. The structure, general policy, and use of the resource center by small groups and classes are discussed, together with the role and work of the library, user training, and effectiveness. The Hungarian study emphasizes the spreading transformation of school libraries into resource centers. A guidebook was prepared in 1987 to promote this transformation, but data included in the study indicate that the transformation has not yet become general. Because the poor Hungarian economy makes acquisition of special equipment difficult, the emphasis must be on good pedagogy. Taken together, the three studies lead to the following conclusions: (1) an increasing number of schools are reaching the point that they have enough audiovisual material to require processing and services; (2) the transformation of school libraries into resource centers is a relatively short process that includes the centralization of printed and non-printed materials in the library, processing, and establishing the school's centralized databank; and (3) the success of the media center depends on changing the attitudes of all people participating in the teaching-learning process, and changing attitudes is time-consuming. (KRN)