Medaka (Oryzias latipes) has been recognized as a potential model vertebrate to which modern molecular genetics can be applied. Recent progress in transgenic techniques emphasizes the importance of the use of medaka in a variety of biological fields, particularly in view of the development of transgenic vectors. The first transgenic medaka was produced by microinjection of DNA into the pronucleus of unfertilized oocytes. Several new methods have since been developed for producing transgenic medaka, and an appropriate method can be selected according to the aims of experiments and application. Transgenic medaka have been used in many fields, including aquaculture, toxicology, developmental biology (phenotypic rescue experiments), and for successful characterization of transcriptional regulatory regions. Here, we describe examples of the application of transgenics in these fields. We also summarize the recent progress in transgenic techniques and transgenic vectors, focusing on the elements and the marker genes that enable identification and/or induction of the expression of exogenous genes in transgenics.