Near-infrared spectroscopy (NIRS) was used to develop a simple and quick technique to differentiate two economically important species, the tobacco budworm,Heliothis virescens (F.), and corn earworm,Helicoverpa zea (Boddie), which are major pests of cotton,Gossypium hirsutum L., in the southern United States. In practice, it is difficult to distinguish the two species during their immature stages using morphological characteristics unless expensive microscopy equipment or trained technicians are available. The current studies demonstrated that the two species could be quickly and readily differentiated during early developmental stages, including egg and young larval (younger than third instar) stages, by using NIRS technology with up to 95% accuracy. NIRS technology could significantly improve pest diagnosis in cotton pest management.