Increasing plant density in maize from 8 to 32 plants/m2, without irrigation, had little effect on the time of ear primordia differentiation but delayed the time of silking (by up to 16 days), reduced the potential grain sites available for pollination and the number of grains pollinated, and increased grain abortion during the grain fill period. In cv LG11 sufficient fertile ears were retained to maintain grain yield throughout the wide range in density, whereas yield fell in Anjou 210 due to barrenness after silking, which was the major factor responsible for the intolerance of this variety to high density. However, in a variety such as Anjou 210, which has a tendency to barrenness under stress, the grain content of the end product would not be affected at the plant densities normally used for maize silage.