As hotspots of biodiversity, oyster reefs fulfil important ecological functions. Being biogenic reef builders, for many animal species they provide food, a substrate for colonisation, and a space to spawn and find shelter, thus increasing biodiversity. By filtering the water they im prove water quality and enhance benthic-pelagic coupling. European oyster (Ostrea edulis) and the oyster banks they form were once widespread in the North Sea. Due to overfishing until the 1920s, the species is considered functionally extinct in the German Bight. The testing and development project RESTORE, supported by the BfN with BMUV funding, is investigating methods for the restoration of the European oyster population in the German North Sea. For the purpose of sustainable population development, the project is working on technological and biological challenges and aspects of nature conservation law, and develops and trials methods for practical implementation as a part of marine nature con servation measures. The preliminary investigation provided the legal framework for the practical testing of measures to restore European oyster in the Borkum Reef Ground Nature Conservation Area (NCA). It helped to establish a comprehensive knowledge and technology transfer network in Europe. RESTORE initiated the creation of the Native Oyster Restoration Alliance (NORA), where European projects for the restoration of the native oyster work closely together. Com prehensive field studies conducted during the preliminary investigation confirmed the funda mental suitability of European oyster for restoration in the German North Sea under the en vironmental conditions that prevail today. The preliminary investigation identified the specific challenge of availability of suitable seed oysters for marine conservation measures and devel oped suggestions for solutions. RESTORE recommended the establishment of a German seed oyster breeding programme for long-term restoration measures. This is now being imple mented funded by the Federal Biodiversity Programme within the context of the PROCEED project. Through extensive laboratory and field experiments, the preliminary investigation identified suitable substrates that can be used in oyster breeding and in the practical imple mentation of restoration measures in the field. In conclusion, the preliminary investigation recommended the construction and scientific in vestigation of a pilot oyster reef in the Borkum Reef Ground NCA. All legal, biological and tech nological requirements have been identified, so that this next step can be carried out as part of the RESTORE main project and subsequently evaluated by scientific monitoring.