One of the more difficult ergonomics problems is determining the operator workloads and the total mill or shop performance resulting from design changes in the operation. Man/machine simulation and experiments with this simulation provide an aiding technique for ergonomic designers. This technique is demonstrated in the case of steel making in the Basic Oxygen Furnace Shop and the Rolling Mill. Modeling with the latest version of SAINT is shown. Experiments are illustrated for different modes of operation, added or deleted equipment, and new technologies in order to find mill and shop performance and the effect of workloads on particular jobs. Experimental strategies and implications are discussed.