Recently, there have been many changes in researches of mathematics education. There is a growing number of researchers who are interested in empirical researches. According to the these changes, there is also an emphasis on methodology of mathematics education. This means that many researchers try to conduct an research using scientific approach. Therefore, new types of research developing mathematics courses recently has evolved as follows: teaching experiment, hypothetical loaming trajectory, design science, developmental research. The aim of this study is to reflect on developmental research in RME and to induce desirable directions for developing our mathematics courses. In order to attain these purposes, the present paper reflects the philosophy of RME, aim, procedure, data collection, data analysis, and justification of developmental research with illustrating a exemplar Based on these reflections, it is discussed that it needs to construct the mathematics curriculum connecting theory and practice in mathematics education, to report the process of developing mathematics courses faithfully, and to develop real mathematics courses after conducting basic developmental researches in order to take scientific app- roaches for developing mathematics courses.