Iowa and other Corn Belt pork producers have become concerned about the potential of very large comnercial or "industrialized" hog operations growing out of economies of size (or cost advantages and scale economies for larger producers). The purpose of this study was to estimate empirically the economies of size associated with specialized nonintegrated swine enterprises in central Iowa. This information can then be used to judge the competitive position of different-sized hog operations in Iowa. Costs were budgeted for 10 levels of production from 25 to 1,000 sows. The prices used for the various items were those that existed in central Iowa in 1970. Three management systems were examined: the pasture, the open front confinement, and the environmentally controlled confinement systems. Each management system consisted of four phases: gestation, farrowing, growing, and finishing.