A recent paper by Cimen and Banks [2004. Nonlinear optimal tracking control with application to super-tankers for autopilot design. Autoniatica, 40(11), 1845-1863] on optimal control system design for oil tanker propulsion and heading highlighted the importance of accurately representing the dynamics of such a vessel. Results presented in that paper are based on a simulation model that provides unrealistic results for an oil tanker of the size considered. Therefore, the results obtained from the simulated ship control problem are not representative of the physical system being considered. In this communication an alternative, more realistic model is presented and discussed with reference to the original publications that define the ship model dynamics. (c) 2006 Elsevier Ltd. All rights reserved.