Recently, the development of nanomedicines is progressing. These are designed to ensure high stability and to optimize the pharmacokinetics in vivo. The polymeric micelles and lipid nanoparticles are typical such examples. Because the unique size-specific interaction with biological systems or biodistribution may have significant impacts on the efficacy and safety of nanomedicines, regulatory science researches of nanomedicines are required. In this review, the authors introduce our initiatives of the regulatory science researches of nanomedicines.