It is very important to improve the efficiency of traction motors to save energy in electric trains. In addition, improving the efficiency is also important to realize a totally enclosed traction motor that requires less maintenance. Therefore, the use of high-efficiency motors is expanding. Many of them are induction motors with high-performance materials; e.g. low-loss electrical steel sheets and low-resistivity conductors. Meanwhile, some of them use permanent magnet synchronous motors, which have higher efficiency than induction motors. In this paper, we will review these recent technologies to improve the efficiency of traction motors and give examples of high-efficiency traction motors in use in Japan. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.