Bombyx mori nucleopolyhedrovirus (BmNPV) DNA was partially digested with BamHI and BglII, or EcoRI, and cloned into the cosmid pWE15. Eight cosmid clones possessing viral DNA fragments with a size range from 34.9 kb to 45.1 kb were obtained, and they covered the entire viral DNA sequence. Using the cosmid library and plasmid libraries obtained previously, physical maps of BmNPV DNA were constructed for EcoRI, SmaI, PstI, SacI and SacII.