This report is a deliverable of MERiFIC Work Package 3: ‘Dynamic Behaviour of Marine Energy Devices’ involving the collaboration of IFREMER (Institut français de recherche pour l'exploitation de la mer) in France and the University of Exeter in the United Kingdom. It is anticipated that the International Electrotechnical Commission’s guidelines Marine energy - Wave, tidal and other water current converters - Part 10: The assessment of mooring system for marine energy converters (MECs) will be published by the end of 2013. Although there are several guidance documents in the literature regarding the mooring of marine renewable energy (MRE) devices, the IEC document is one of the first to be produced on this subject, with guidance also available in documents produced by Det Norske Veritas. This document is intended to provide a concise introduction to mooring systems for MRE devices with reference given to guidelines and standards which may be applicable to the design of moorings for marine renewable energy (MRE) devices. The document begins by setting the scene to give background on the fundamental differences between conventional offshore equipment and MRE devices. In Section 2 design considerations are introduced, including cost, geometry and the importance of conducting risk analysis. Section 3 then gives an overview of moored system numerical modelling. Key findings of the report are then summarised in Section 4.