Summary In a world where global warming has become an every day expression, the focus on alternative energy sources is rising. The use of wind power has long been an environment friendly option to other more pollutional energy sources. World wide there are industrial environments engaged in concept development for floating offshore windmills. The technical challenges for risers and mooring lines continue to increase with the development towards larger water depths and ever expanding areas of use. These will normally not be built on extremely deep water, but depths between 100 – 300 meters are seen as realistic. This thesis presents the theory needed to perform a static and dynamic analysis of a mooring line thought used on a floating windmill at 300 meters water depth. After a short description of how to build a static and dynamic element model, the analysis is carried out. Results from both the static and dynamic element solution are presented, as well as results from an industrial simulation tool, SIMO. The dynamic solution is divided into one analysis with and one without damping. A comparison between the different analysis and a discussion of possible deviation sum up the results from the calculations.