Feeding activity, growth, and survival of soybean looper,Pseudoplusia includens(Walker), larvae fed foliage from nonnodulating soybean,Glycine Max(L.) Merrill, plants supplied with different rates of nitrogen (N) fertilizer were examined. Foliage was obtained from the non–nodulating isoline ‘Lee’ soybean beginning at the V8 growth stage (46 d after planting) and continuing through initiation of bloom. Plants were grown in pots fertilized with four sequential applications of five rates of N fertilizer (5.25, 21, 42, 84, and 168 kg N/ha as NH4NO3) and from nonfertilized plants. These six treatments resulted in foliage N concentrations that ranged from 10 to 33 mg/g dry weight and chlorophyll concentrations that ranged from 0.5 to 1.7 mg/g fresh weight (51–50 d after planting) during the feeding bioassay. Foliage from nonfertilized control plants and those fertilized with 5.25 and 21 kg N/ha were low in N(≤12 mg/g) and caused 100% mortality when fed to soybean looper larvae. Foliage from plants fertilized with 42 kg N/ha contained 17 mg N/g dry weight and resulted in moderate levels of mortality (55%), whereas the higher N rates (84 and 168 kg N/ha) resulted in foliage N concentrations of 22 and 33 mg/g dry weight and ≥90% survival. Although the highest three foliage N concentrations were sufficient for survival of soybean looper larvae, differential effects on development of larvae were observed. Greater number of stadia, lengthened duration of the larval development period, and greater foliage consumption were observed with each reduction in foliage N from 33.4, to 22.4, to 16.9 mg/g, but ultimately, similar maximum larval weights were achieved. These three factors appear to be mechanisms tbat allow the soybean looper to compensate for reduced N and may explain how this species maintains itself on such a wide range of hosts (73 plant species in 29 families) including noncultivated species.