The input-output analysis method was applied for forecasting the total Korean petrochemical outputs for the years of 1974, 1978, nd 1992. The methods of measuring the extent of impact of the growth of petrochemical industry on other industrial sectors, and vice versa, were developed mathematically by defining the influence coefficient, sensitivity coefficient, and induced production. A simple method of forecasting the input coefficients and the elements of the final demand vectors, in absence of a sufficient amount of data, was also suggested. The computer analysis was carried out on a 90×90 technology matrix which was derived from a reorganized input-output table in which the original organic chemicals sector in the 1970 56-sectorial interindustry transactions table of the Bank of Korea was subdivided into 64 new major petrochemical products.