This paper analyses the main consequences for the seaport efficiency of an access regime recently introduced by the Peruvian regulator for the public transportation infrastructure (OSITRAN). Its objective is to make competition viable for services that use, as input, transport infrastructure controlled by a monopolist. It is based on two theoretical contributions, the ‘Coase theorem’ and the ‘Demsetz approach’, and minimises the government intervention risk. Both port operators and providers of port services now have incentives to negotiate conditions of access, which permit competition, or to compete for an exclusivity right when this is desirable. If the parties do not reach an agreement within a reasonable time, the Regulator can enact an access mandate that may punish any of the parties, creating incentives for them to reach a Nash Equilibrium. The model seems to be generating productive and allocative efficiencies in port services, thus contributing to a potential reduction in Peru's maritime transport costs. © 2003 Palgrave Macmillan Ltd. All rights reserved.