A pastoral farm is a complex agro-ecosystem that produces agricultural outputs such as milk, meat and wool. Detailed consideration of the complexities of agro-ecosystem components, and the interactions between these components, may be best approached with simulation modelling. We reviewed nine simulation models (APSIM, EcoMod, FASSET, GRAZPLAN, GPFARM, Hurley Pasture Model, IFSM, LINCFARM, and WFM) used primarily for research of grazing systems. GrassGro (one of the GRAZPLAN suite of decision support tools), LINC-FARM, and WFM had particular strength in their simulation of animal production and farm management. The strengths of APSIM, EcoMod and FAS-SET lie in their simulation of soil nutrient dynam ics, crop or pasture production and spatial variations in soil properties. The Hurley Pasture Model has particular capability to model nutrient cycling in the presence of climate change. The IFSM includes a comprehensive representation of machinery. GP-FARM can be used to predict forage production of different plant functional groups.We suggest that more emphasis could be placed on including the effects of pests and diseases on pasture production and animal performance, more detailed representation of management practices, inclusion of more mechanistic voluntary feed intake and rumen processes and including the effect of specific genes and gene-by-environment interactions on plant quality and yields, nutrient use and animal performance. The Common Modelling Protocol, used in APSIM and the GRAZPLAN suite, may enable the development of a powerful and flexible pastoral agro-ecosystem model which incorporates newly developed modules of the nature mentioned above.