In order to improve convenience for investors through competition among stock exchanges, operation of Proprietary Trading Systems (PTS) was authorized as a form of securities business under the Securities and Exchange Act. The Japanese PTS is equivalent to ATS (Alternative Trading System) ECNs (Electronic Communications Network) in the United States and MTF (Multilateral Trading Facilities) under MiFID in the EU. In 1998, ATS ECNs had already started in the United States and Japan’s PTS followed the US model. Telecommunication and information technologies and computer technologies made PTS possible, and PTS make the border between the market and brokers ambiguous. Traditional regulations on broker-dealers and stock exchanges will inevitably be reviewed and regulations on securities markets will have to be reformed.