To assess the ability of the transposable element Minos to act as a vector for genetic manipulation of the silkworm Bombyx mori, an extrachromosomal transposition assay based on three plasmids was performed. The three plasmids - helper, donor and target - were co-injected into preblastoderm embryos. Low molecular weight DNA was extracted from the embryos at the stage of blastokinesis and used to transform Escherichia coli. High frequency of transposition was observed in the presence of a helper plasmid possessing an intronless Minos transposase gene, whereas transposition did not occur in the presence of a helper plasmid with the intron-bearing transposase gene. Sequence analysis of the insertion sites showed that Minos always inserts into a TA dinucleotide. Although the insertions are distributed throughout the target gene, there was a preference for certain insertion sites. However, no consensus could be identified in the sequence flanking the target site. The results strongly suggest that the transposable element Minos has the potential to be used as a vector in the silkworm and probably in other lepidopteran insects.