The mtDNA RFLPs were investigated to analyze phylogenetic relationships and genetic similarity among five silkmoths Bombyx mori(Chinese strains, Japanese strains), Bombyx mandarina, Antheraea yamamai, and Antheraea pernyi. Genome sizes of mtDNA of the silkmoths were determined 16.0±0.5kb by total length of all the restricted fragments and size variation was not detected. Of the fourteen different restriction endonucleases used, BamHI, HindIII, PstI, EcoRI and XbaI, showed RFLP. Among them only HindIII showed RFLP between Bombyx mori and Bombyx mandarina. Matrix for genetic similarity was constructed by UPGMA (Unweighted Pair Group Method with Arithmetic mean) method using sixty eight mtDNA RFLP markers obtained from the silkmoth species digested with above fourteen restriction endonucleases. Genetic similarities were varied from 0.227 to 1.000 with its average of 0.498. However, genetic similarity between Bombyx mori and Bombyx mandarina out of five silkmoths was determined to 0.848 which indicates highly homogeneous genetic background. Our results suggest that RFLP analysis of mtDNA is a useful tool to elucidate phylogenetic relationships among the silkmoths.