In order to analyze the linkage of phenotypic traits in the field of molecular biology, marker sequences which display polymorphism are a prerequisite. Since it is generally accepted that interspersed repetitive sequences are highly variable, we considered that these sequences would be suitable as marker sequences. Therefore, the interspersed repetitive sequences from swine genomic DNA have been cloned and characterized. The cloned repetitive sequences were found to belong on the PRE-1 family. The homology analysis of those sequences indicated that they varied in the range of 68 to 85%, and that an arginine t-RNA gene was their progenitor. The localization of PRE-1 sequences on chromosomes was investigated by in situ hybridization which revealed that the PRE-1 sequences were distributed unevenly all over the chromosomes. These findings indicated that the PRE-1 sequences could be used as suitable linkage markers.