Silkworms sex determination drew high attention from researchers. Sex chromosomes on the silkworm are of ZW type for females and ZZ type for males. Chromosome W plays an important role in sex determination. Although several molecular linkage maps have been constructed for silkworm, very few markers are discovered on the W chromosome. In order to look for molecular markers and to further locate the Fern gene on chromosome W, we used genomic DNA from both female and male larvae of a silkworm strain named 937 as PCR templates for RAPD amplification with 200 arbitrary 10-mer primers. The amplification results showed three female-specific bands, namely ${OPG-07_496}, {OPC-15_1,660} and {OPE-18_1,279}$. Further verification, however, revealed no band from OPG-07 and OPC-15 in either sex in the strain 798, but OPE-18 provided female-specific band in the strains Suluan7 and C108, and absent in both males and strain 798. This indicates that the bands from ${OPG-07_496} and {OPC-15_1,660}$ are probably female-specific in strain 937, and the band from OPE-18 was probably amplified from a common segment shared by most strains. The genomic DNAs from OPG-07 and OPC-15 were cloned and sequenced. Sequence analysis showed that the DNAs from OPG-07 and OPC-15 have high identities with the retrotransposable elements, and DNA from OPC-15 contains a portion of sequence which probably encodes an eukaryotic translation initiation factor 4E binding protein (eIF4EBP).