Modeling and simulation are essential tools for the design and analysis of container terminals. A computer model can emulate the activities at various levels of details and capture the essential interactions among the subsystems. Analysis based on the simulation is particularly useful for designing new terminals, making modifications to existing terminals, and evaluating the benefits of new resources or impacts of operation policies. We present a scalable tool that integrates all the activities of a terminal. The system incorporates methods to generate realistic vessel arrival patterns and can track the moves of millions of containers from their arrival to departure. The simulation system is applied to analyze three container terminals in this region, and it was found to be effective in replicating realistic operations as well as in conducting capacity evaluations. KEY WORDS Modelling, simulation, capacity of container terminals.