An emerging issue to privatizedinfrastructure sectors is how regulators should deal withproposed mergers that could potentially increase marketpower and lead to anticompetitive behavior. This note looksat the issues in the port sector, discussing the regulatorytreatment of vertical and horizontal mergers. It focuses onArgentina, one of the first countries to concession itsports. In the early 1990s Argentina restructured andprivatized its port system. As part of this process thegovernment transferred ports to the provinces, which couldchoose to operate, concession, or close them. The note alsoanalyzes the consequences of allowing a vertical mergerbetween a terminal operator and a maritime transport companyand the pros and cons of explicitly prohibiting horizontalmergers between terminal operators.