The aim of this work is to describe an eddy current non-destructive testing system employing Giant Magnetoresistive (GMR) sensors. GMR sensors are solid state devices capable of measuring the magnetic flux density. The use of GMR sensors in the framework of eddy current testing is motivated by their intrinsically high sensitivity, large bandwidth and low cost. This paper is specifically focused on the development of a GMR based probe integrated into an eddy current testing system for detecting the presence of millimeters size cracks in highly conductive materials such as Aluminum.