A method is described for steering of an un-manned ocean vessel (10), where the vessel comprises a hull (12), a self-tacking wing sail (16) for propulsion, a keel (18) for direction stability and a rudder (20). The method comprises the steps: to set the rudder (20) and the sail (16) so that the vessel (10) holds a stable direction with regard to the wind at a given rudder deflection, a) to check the position of the vessel (10) with the help of an electronic steering system (22) on board, and if it is registered that the vessel (10) is not getting any nearer its destination, b) adjust the rudder (20) to set a new, arbitrary course, where the course is chosen from among a number of pre-determined course changes, c) check again the position of the vessel (10) with the help of the electronic steering system (22) and if it is registered that the vessel (10) has got nearer its destination, d) to let the vessel (10) continue on the same course, and e) to repeat said check of the position of the vessel (10) and the steps a) to d) at regular intervals.