Econometric procedures are employed in an analysis of N.S.W. cattle and sheep producers' decision-making regarding the annual supplies of beef, veal, lamb, mutton and wool, and annual changes in the inventory levels of beef cows, dairy cows, steers, adult sheep and ewes mated to British breed rams. A simultaneous equation model containing fourteen stochastic equations is specified and estimated using annual data for the period 1953-4 to 1970-1. A set of derived reduced form functions are employed in a study of some dynamic behavioural relationships in the cattle and sheep sector. The estimated model is used to analyse some effects on prices, quantities and inventory levels of the imposition of a (10 cent per kg) tax on beef exports.