The 155 m high Goescheneralp earth-core rockfill dam will be heightened by 8 m with the aim of increasing the reservoir storage volume by 14.5% to 87 Mio m
3. Therefore, the filter materials of the existing dam were reviewed and filter materials for the dam heightening were designed. In this paper the existing Goescheneralp dam is briefly described and filter test data are presented. The design of the dam heightening is presented and discussed. Emphasis is given to the filter materials including a comprehensive review of state-of-the-art filter criteria.