The actin-binding protein profilin cDNA was firstly isolated from the lepidopteran insect, silkworm Bombyx mori. The B. mori profilin cDNA contains an open reading frame of 378 bp encoding 126 amino acid residues and possesses three cysteine residues. The deduced amino acid sequence of the B. mori profilin cDNA showed 80% identity to Apis mellifera profilin and 72% to Drosophila melanogaster profilin. Northern blot analysis showed that B. mori profilin is highly expressed in epidermis and less strongly in silk gland. In addition, Northern blot analysis revealed the presence of B. mori profilin transcripts in all tissues examined, suggesting that B. mori profilin gene is expressed in most, if not all, body tissues.