It has been predicted that production rates as high as 4000 tpd of hot metal will be achieved by some blast furnaces by 1972. Based on data from the 10 blast furnaces in the United States that are topmost in production, the operating improvements necessary to attain this goal are discussed in detail. The more important improvements include:increase in hot-blast temperature, incorporation of more flux in the agglomerates, greater uniformity in the chemistry and size-consist of coke and iron-bearing materials, increase in top pressure, and oxygen enrichment of the blast. In addition, such factors as furnace and casthouse size and charging operations are discussed in relation to achieving the goal.