Abstract: A guidance system and method for keeping a tunnel boring, machine continuously on a plan line. The guidance system requires no machine operator calculations and provides the boring machine operator with a graphic display of past, present and projected positions of the boring machine from a horizontal and vertical perspective. The system uses a laser beam transmitter placed to the rear of the tunnel boring machine along with a front opaque target with a horizontal and vertical cross-hair and a rear transparent target with a horizontal and vertical cross-hair. The front and rear targets are disposed on the front and the rear of the boring machine. Also, an on-board programmable computer is installed on the boring machine for imputing data as to horizontal offset and vertical offset readings from the front and rear targets as the boring machine advances forward. Typically the boring machine moves forward in increments of four feet with offset readings taken by the operator after each increment.