A good business forecasting or demand forecasting can contribute greatly to a nation's economic planning. For a desirable economic planning, it is necessary to be able to predict future business conditions. An accurate demand forecasting for many goods can help achieve the nation's economic planning by eliminating material wastages and controlling unnecessary oversupplies of material which are caused by unbalances in the demand and supply relationships. In an attempt to satisfy these needs, the present paper purports to conduct a demand forecasting （1976-1981） for the overall products of domestic petro-chemical industry. Thus the following methods are used as the appropriate approach for this purpose.
（1） First, as the goods which are needed for this study, 18 items of final products (ten items of synthetic resins, four of synthetic fibers and four of synthetic rubbers) and 32 items of intermediate products and raw materials are selected among the overall products of the industry.
（2） A multiple regression analysis is conducted to forecast demand for the final products.
（3） Manufacturing consumption coefficients and modifier coefficients are used to forecast demand for the intermediate products and raw materials.