Experiments at the Ohio Agricultural Experiment Station are reported, comparing corn planted at different rates, in hills and drills, and on soils of four different productivity levels. The results support the findings of other workers in indicating that as growing conditions become more favorable the optimum stands are higher. They also show that adapted hybrids as a group have higher optimum stands than do open-pollinated varieties of comparable seasonal requirement, probably because of the greater vigor of the hybrids. The difference between the two optima amounts to about 1,800 to 2,000 plants per acre under favorable growing conditions. The effect of stand on grain yields is much greater at high than at low productivity levels. It would follow that where different soil treatments are being studied in field experiments, the planting rate should be the one expected to give an optimum stand for the better treatments. Such a stand would affect the poorer treatments relatively little but would make it possible to measure the full productivity of the better treatments. At optimum stands, the air-dry ears averaged a little more than half a pound each. The great pound-sized ears so often displayed in corn exhibits and sales literature merely indicate inefficient use of a favorable environment for corn. Furthermore, at optimum stands, competition tended to throw some of the plants into near or complete barrenness. Thirty-three hybrids averaged 113.7 bushels per acre with 13% barren or near-barren plants in 1935; and at the rate considered optimum, 60 hybrids averaged 89.1 bushels with 11% barren or near-barren plants in 1936. Tillering decreased rapidly as stands approached the optimum. At comparable stands tillering was much heavier in drilled rows than in checkrowed hills. In 1941 (Table 2) the much higher incidence tillering in the thinner drilled rows was not accompanied by higher yields than in the checkrowed hills of comparable stands. The experiments revealed no consistent relation between rate planting and resultant stand in terms of percentage of seed planted. Weeds were much more abundant where stands were thin in an experiment in 1943. The test weight of grain did not appear to be affected by differences in stand. There are several unfavorable effects of the heavier stands (Table 5). The harvested crop is less attractive because of the smaller ears and the higher proportion of nubbins. The silking period for a stand of five plants per 42 inches of row-space was roughly 2 days later than for a stand of three plants in the same space. This would probably delay maturity by four or five days. Conceivably the less abundant mineral nutrient supply for the individual plants could affect the quality of the grain adversely. The most serious effect of the heavier stands is in the higher incidence of stalk breakage.