SINCE the introduction of field shelling of corn by combines, many farmers have changed from ear-corn harvesting to a high-moisture, field-shelling system. A field survey (USDA 1971) in the Corn Belt indicated the continued shift to combines for harvesting corn. The portion of acreage harvested by corn heads on combines reached 69 per-cent in some midwestern states for the 1971 season. The combine approach has gained such favor because combines are universal types of harvesters, which may be equipped with different head attachments, and, when appropriately adjusted, can be used to harvest all types of grains. Field combining of corn has brought into focus the problem of mechanical damage to corn kernels. Industry and re-searchers (Byg et al. 1966, Cooper 1968, Hall and Johnson 1970) have directed their efforts to improve the shelling performance by establishing optimum operating parameters, yet shelling damage continues at objectionable levels. Several research workers (Brass 1970, Fox 1969, USDA 1967) have developed a new shelling mechanism. The experimental shellers shell corn with less damage than conventional shellers, but inherent limitations and performance problems have been encountered. It thus seems that the full potential of the conventional cylinder-concave mechanism in shelling corn has yet to be realized. Basic research is needed to indicate where damage occurs and what modifications are needed to substantially reduce the level of damage. This must be done without adversely affecting the overall performance of the machine. The literature reviewed showed lack of quantitative evaluation of corn-kernel separation and damage distribution along the concave. Research was conducted with the specific objectives of investigating the distribution of through-put and mechanical damage of shelled corn in the combine-shelling mechanism (Mahmoud 1972)