Nucleopolyhedroviruses (NPV) are considered among the most promising microbiological control agents for Spodoptera littoralis (Boisduval) (Lepidoptera Noctuidae). In a first laboratory experiment, a new SlNPV-based formulation was compared with a conventional Bt toxin product in order to evaluate its potential role as bioinsecticide for the short-term control of S. littoralis. Both formulations were tested on second instar larvae at the recommended dosages for treatment of vegetable crops. Four days after the treatments, Bt toxins caused higher mortality and significantly reduced leaf damages; on the contrary no significant differences were recorded between SlNPV and control treatments. Further investigations were carried out to assess the impact of SlNPV on S. littoralis over time. The mean lethal time (LT50) for second instar larvae treated with SlNPV was 7.32 days and it was significantly shorter than LT50 in control group.