The Spanish banking sector has been subject over recent years to a twin process of long-term structural change: strong deregulation and a major opening-up to the external sector. This study analyzes the impact that the change in the regulatory environment has had on the level of internal rivalry in the sector, with the consequent increase of competitive pressure and its impact on operating costs. The research highlights that the most dynamic banks have used the opportunities that have opened up through deregulation and European integration to generate additional business in new products and markets.