Due to the successes of past breeding efforts aimed at improving stress tolerance and input responsiveness, modern maize (Zea mays L.) hybrids have acquired the ability to produce high grain yields when grown at high plant populations.  Yet at high plant densities, intraspecific competition among plants is intense for limited soil resources such as water and nitrogen (N).  Mineral N availability may be more essential for proper maize growth and development at high plant densities than at low plant densities.  The objective of this study was to examine both per-plant and canopy-level, morpho-physiological responses to N application (0, 170, and 340 kg N ha^-1) at multiple plant densities (54,000, 79,000, and 104,000 plants ha^-1) for a single, modern genotype (hybrid Pioneer 31G68), with a particular emphasis on these responses when intraspecific competition was most severe (0 kg N ha^-1, 104,000 plants ha^-1).  Morpho-physiological parameters examined at various stages of vegetative and reproductive development in 2005 and 2006 on both a per-plant and canopy-level basis included plant height, stalk diameter, leaf area index (2006), anthesis (2006) and silking date, SPAD, grain yield, total kernel number, and kernel weight.  In general, a higher N rate and a reduced plant density facilitated greater plant height and stalk diameter values during both vegetative and reproductive development, reduced flowering delays, and delayed leaf senescence and photo-assimilate translocation.  Improving resource availability through either N application or lower plant populations enhanced both per-plant and per-unit-area grain yield and reduced per-plant grain yield variability.  In this presentation, we will further discuss N rate and plant density effects on the morpho-physiological dynamics of maize at both the per-plant and canopy level.  Particular emphasis will be placed on the effects of N limitations on these dynamics at the highest plant density (104,000 plants ha^-1).