Initially, these four exchanges operated independently. However, the Spanish Securities Market Act in 1988 envisioned a single, unified system and the four exchanges were interconnected a year later. At the outset, there were five companies operating within the market and they were grouped together using the Computer Assisted Trading System (CATS), a software adapted from the Toronto Stock Exchange. In 1995, the Spanish Stock Exchange Interconnection System (known as SIBE) replaced CATS and remains in use to this day. And in 2001, following Spain's entry into the European Union, these four exchanges were definitively unified.
This market brings together more than 130 companies, including IBEX-35 stocks and other smaller companies that are not listed on the IBEX-35. It is supervised by the Spanish National Securities Market Commission (CNMV) governed by BME, which is also indirectly responsible for settlement and clearing.