Apparatus and method for a directional drilling system is disclosed wherein a concrete pit is poured at a reference entry angle in the earth so that a drilling platform cartridge inserted into the concrete pit is set at the desired entry angle. A frame, including elongated guide ways extending between ends of the platform cartridge, guides a carriage that advances a drill string through the earth at the reference angle. Preferably, a drilling head at the end of the drill string and the remainder of the drill string are rotated by a drive motor carried on the carriage. A drill bit and drill bit motor are mounted coaxially and eccentric with respect to the drilling head. The center axis of the drill bit and drill bit motor, and the center axis of the rotating drilling head are offset and define a known relationship. The offset relationship between the center axis of the drill bit and drilling head defines an eccentric position in which the drill bit overcuts relative to the outside diameter of the drilling head in an eccentric position. As long as the drilling bit and drilling head rotate simultaneously, movement of the drill string is controlled generally in a straight line. If rotation of the drilling head is stopped, the drill string is steered in the direction of the eccentric position of the drill bit since there is no clearance on the opposing side of the drilling head.