The rationale for the development of a national experiment within the Sustainable Grazing Systems (SGS) Key Program is outlined, together with a brief description of the sites, their focus of study and the results of a pre-experimental modelling process at three locations. The location and pasture types being studied for the six sites in the national experiment (North-West Slopes, NSW; Tablelands, NSW; Wagga Wagga, NSW; North-East Victoria; Western Victoria, and Western Australia) are described.