Several farm sector econometric models are reviewed initially and the aggregation problem highlighted. A thirty-equation model of the Australian agricultural sector is specified in which farm output, stocks and exports and the domestic demand for farm products are endogenous, as well as farm, export and retail prices. Disaggregation is into food and non-food components of unprocessed output, and the processing of food is traced through to final demand. The model is estimated by a modified 2SLS procedure using quarterly data covering the period 1960-1970.