Abstract: A drilling rig comprising a base; and an A-frame carried by the base. The A-frame has left and right hydraulic mast cylinders with pistons in the cylinders. The rig also has a mast pivoted on the base and capable of being raised from a horizontal position to a vertical position. The mast has left and right pads adapted to respectively contact the left and right mast pistons before the center of gravity of the mast passes a point directly above the axis of rotation of the mast. The rig also has drawworks adapted to raise the mast about its axis of rotation; and has a hydraulic control system comprising means for synchronizing the movement of the left mast piston with the right mast piston.