Technical Abstract: Nutritional (i.e., total proteins, amino acids, glucose, total non-structural carbohydrates [TNC], amino acids to TNC ratio) and biochemical (i.e., peroxidases and lipoxygenases) properties of 3 corn (Zea mays) germplasm (i.e., inbred lines AB24E and Mp708, and a local selected population FAW7050) with various degrees of resistance to Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) injury were examined. Physiological changes (i.e., photosynthetic rates) were also examined in an attempt to explain nutritional and biochemical dynamics among corn germplasm and between insect-damaged and un-damaged corn plants within a germplasm. Results from both greenhouse and field studies showed that AB24E was susceptible, while FAW7050 and Mp708 were resistant to S. frugiperda. Susceptible AB24E and resistant FAW7050 had greater levels of constitutive total protein than resistant Mp708. Spodoptera frugiperda feeding induced the increase of total protein in Mp708 and FAW7050, but not in AB24E. Mp708 and FAW7050 had higher levels of amino acids than AB24E. Constitutive glucose contents of FAW7050 and Mp708 were over 24% greater than that of AB24E. Furthermore, S. frugiperda injury greatly elevated glucose contents of Mp708 and FAW7050. AB24E and Mp708 had higher amino acid to TNC ratio than FAW7050. Mp708 had greater constitutive peroxidase activity than AB24E and FAW7050. Spodoptera frugiperda feeding on AB24E increased peroxidase activity. Resistant Mp708 and FAW7050 had greater photosynthetic capacities than that of AB24E because the two former germplasm had greater A/Ci curves (indicators of light-independent reactions of photosynthesis). SDS-PAGE electrophoresis showed no significant difference in banding patterns of total protein among control and S. frugiperda-injured three corn germplasm, while intensity of bands did show difference at 29 kDa.