Summary: Several forms of telecommunication infrastructure sharing exist, including co-leasing, network interconnection, and local loop unbundling. Such sharing arrangements are increasingly required by regulations in order to facilitate access to facilities, ensure competition, and achieve gains in productivity that will be passed on to end users. However, the financial implications of infrastructure sharing, including in terms of passing on productivity increases to the end user, have not been proven. The debate is still open as regards the right balance between regulation of infrastructure sharing and investment incentives.