Abstract: A mobile crane having frame structure supporting a boom and turret unit between the front and rear wheel axles of the crane is provided with four outrigger arms which are extensible to present an extended perimeter X-shaped pattern. The outrigger arms are each swingably attached to the crane for swinging movement from retracted positions adjacent the turret of the crane, to extended X-pattern defining dispositions where the ground engaging pads of the two forwardmost extended outrigger arms are generally aligned with the axis of the front axle of the crane, and the ground engaging pads of the two rearmost outrigger arms are generally aligned with the axis of the rear axle of the crane. Each of the outrigger arms is constructed such that the outer pad supporting ends move through an essentially upright path of travel as they approach, move toward and then move below ground level at the wheels of a crane.