Lysozyme is one of the components of the innate immunity of the insects. The lysozyme has been isolated by heat treatment, cation exchange, and reversed­phase chromatography from immunized hemolymph of last instar larvae of Spodoptera litura. The hemolymph immunized with the insect nonpathogen, Escherichia coli was collected 2 days after the abdominal injection. The molecular weight of Spodoptera lysozyme was estimated to be about 15 kDa by SDS­PAGE and it is great similarity with Agrius lysozyme, which recently purified from larval hemolymph of Agrius convolvuli.