In order to understand the diversity and genetic relationships of silkworm strains preservedin Korea, we genotyped 78 Bombyx mori strains (Bombycidae: Lepidoptera) originating fromJapan, using eight polymorphic microsatellite loci. We obtained per-locus allele numbersranging from 5 to 16 (with an average value of 9.1), per-locus observed heterozygosityranging from 0.13 to 1.00, and per-locus polymorphic information content ranging from 0.36to 0.77, indicating that some loci are highly variable. Phylogenetic analysis with the eightconcatenated microsatellite loci showed no clustering based on known strain characteristicsand origin. Nineteen strain-specific apomorphic alleles, which discriminated 16 of the 78silkworm strains, were obtained from eight loci. These strain-specific alleles can thus beutilized for routine discrimination of strains from Japan, without any further typing of otherloci. Homozygotes were also observed at some loci (27 of 118 genotypes), which can alsobe used to discriminate several strains by typing a few loci. These results showed that eightmicrosatellite loci described herein were sufficiently variable to discriminate among the 78silkworm strains we examined, and may be useful for future investigations of this economicallyimportant species.