A comparison on the larvicidial activity of four commercial bacterial and viral bioagents, Profect®, Virotecto®, Viroset® and Protecto® were evaluated on the 2nd and 4th larval instars of Spodoptera littoralis (Biosd.). The LC50 values showed 1.35, 1.52, 1.57 and 1.61 mg/ ml against 2nd instar larvae, respectively. On the other hand, the LC50 values recorded 2.03, 2.5, 2.72 and 3.01 mg/L. on 4th instar larvae of S. littoralis using the above mentioned commercial bioagent products, respectively. The effect on four isozymes, i.e., ,  esterase (EST), glutamate oxaloacetate transaminase (GOT), malate dehydrogenase (MDH) and alcohol dehydrogenase (ADH) were evaluated. The obtained results indicated differences in the activity of the isozymes in treated 4th instar larvae as compared to untreated larvae.