Phytophagous insects cause significant economic damage to soybean [Glycine max (L.) Merr.] throughout the southern USA, but soybean plant breeders have the option of utilizing insect resistant germplasm. This study was conducted to determine the inheritance of resistance to the soybean looper [Pseudoplusia includens Walker] in soybean. The insect‐resistant breeding line D86‐3429 and the more susceptible cultivar Braxton were used to produce the F1, F2, BC, and BCS populations necessary to conduct the genetic studies. Defoliation occurring in 0.068‐ha field cages in 1990 and 1991 from insect releases was estimated by the whole plant visual rating method in 1990 and the partitioned plant average visual method in 1991. The data from the preliminary study in 1990 showed a trend towards quantitative inheritance, therefore the 1991 data were analyzed quantitatively. Mather's scaling test was applied to the data generated from each of two cages, and the results indicated that generation means depend only on additive gene effects. Utilizing Hayman's methodology in the generation means analysis, an epistatic effect was suggested but the primary effect is assumed to be additive as was indicated in the scaling test. Estimates of gene numbers indicate that the two parents differed by two genes for resistance to soybean looper. Heritability for resistance was estimated to be 63%; therefore, a breeder should be able to make progress by selecting in the F2 or F3 generations.