Gloverin is an antibacterial peptide which has been previously isolated in Hyalophora gloveyi, and is known to exert an inhibition effect on the growth of Gram-negative bacteria (GNB). When the expressed genes in the immunized Bombyx mori were screened, gloverin like gene (BmGLP) was found and it was thought to respond against the bacterial invasion. This study presents some data about the gene organization and expression of this candidate for a novel antibacterial peptide in Bombyx mori. The complete sequence, which was determined via RACE, revealed that this BmGLP was identical to the recently reported clone BmGloverin2 mRNA. The transcription of this gene was increased transiently, but to a high degree, around 7 similar to 11 hours after infection, as evidenced by the results of Northern blotting hybridization analysis. Based on the tentative coding sequence, we amplified the genomic sequence and determined that the gene harbored 3 introns. Interestingly, we found retrotransposon relative sequences in introns 1 and 3. Both Southern blotting analysis and sequencing data indicated that the BmGLP2 gene had another relative- or pseudo- sequences in its genome. We also attempted the generation of recombinant peptides in a prokaryotic cell system, but we obtained only truncated peptides and were unable to determine the existence of. any antibacterial activity with the cell extract under physiological conditions. In further studies, the expression system and activity test conditions should be made more representative of the actual insect organism. Finally, we have proposed the possibility that some type of evolutionary link connects retrotransposons activity in insect immunity gene variation.