Personalized medicine offers a custom-made treatment for each patient directed by information of individuals genetic variation. Despite plenty of information about human single nucleotide polymorphisms (SNPs) and gene expression profile, predicting functions of genetic variations in humans is still a difficult task. Genetic analysis using experimental animals is possible to provide information about the functions of genetic polymorphisms over experimental invention in humans. In particular, inbred strains established from wild mice are valuable resources for analyzing functions of genetic polymorphisms. In this article, first I describe history of inbred strains derived from Japanese wild mice, Mus musuclus molossinus. Next, I discuss a mouse model for hyperlipidemia, which was isolated from a colony of Japanese wild mice. Interestingly, the hyperlipimic phenotypes are varied in congenic strains on other genetic backgrounds, reflecting phenotype variation of hyperlipidemia in human populations. Thus, further genetic analysis of Japanese wild mice can contribute to functional analysis of human genetic variation leading to personalized medicine.