Recent studies identified diverse RNAs including noncoding RNAs and their various action mechanisms in the cells. These RNAs regulate a variety of cellular pathways and are therefore expected to be important targets for the treatment of human diseases. Along with their extensive functional studies, RNA-based therapeutic techniques have developed considerably in recent years. After years of research and various trial and error, antisense RNAs and small interfering RNAs-based drugs have been developed and are now being used in the clinic. In addition, active research is ongoing to develop drugs based on RNA aptamer and messenger RNA. Along with the development of these RNA-based drugs, diverse strategies have been developed to transport RNA drugs into the cells efficiently. RNA therapy has many advantages over existing small molecule or monoclonal antibody-based therapies, including its potential to target all genes in the cells. This review will introduce the history of RNA therapy, and explain the basic concepts of RNA therapy and RNA-based drugs on the market or clinical trials. In addition, the future potential of RNA therapy will be discussed.