The behaviour of an instrumented section of a full-scale geogrid reinforced embarkment constructed on a very soft deposit of peat overlying organic silt is examined. The results of field monitoring are reportd together with engineering properties of the soils obtained from laboratory tests. The behaviour was analyzed using the finite element method, and the calculated performance is shown to be in good agreement with that observed.Key words:geogrid, reinforcement, embankment, peat, organic silt.