The RAPD technique was used as a tool for setting up a convenient and standard protocol to determine the interspecific variation between the two strains (laboratory and resistant) of Spodoptera littorals and estimate the intraspecific variation within each strain after treatment. Five (OPA-7, 10, 16, OPB-15 and 20) out of ten primers gave clearly differences among the two strains on the basis of the amplified product patterns, These primers generated 296 fragments The comparison between the two strains of S. littoralis showed differences in the sizes and numbers of the amplified fragments per primer for each strain and each treatment, indicating a high degree of variability between them. The primers OPA-7,16, OPB-15 and 20 gave band patterns which revealed that, there was some degree of divergence between the genome of untreated and treated larvae, higher than primer OPA-10.