Following privatisation, ports face an immediate need to set their prices. For this, they should assess their strategic environment, including: (a) the complex, network-like structure of their port system consisting of principal and intermediary parties; (b) the flow of services and related charges among the above-mentioned parties; (c) the differentiation and price discrimination in the market for port services; (d) the high concentration on both the demand and supply sides of this market; and (e) the mixture of competitive and cooperative behaviours among market agents. The methodology for price setting presented in this paper is based on a systematic assessment of the strategic environment. The methodology employs two novel diagnostic tools: a charge-flow diagram for analysing the allocation of port charges among principal and intermediate parties, and a game tree for analysing the port/competitors, action/reaction dynamics of the oligopolistic market. The methodology is discussed and illustrated using the case of the Port of Cartagena, Colombia.