This work presents an eddy-current testing system based on a giant magnetoresistive (GMR) sensing device. Nondestructive tests in aluminumplates are applied in order to extract information about possible defects: cracks, holes and other mechanical damages. Eddy-current testing (ECT) presentsmajor benefits such as low cost, high checking speed, robustness and high sensitivity to large classes of defects. Coil based architecture probes or coil-magnetoresistive probes are usually used in ECT. In our application theGMRsensor is used to detect a magnetic field component parallel to a plate surface,whenan excitationfield perpendicular to the plate is imposed.Aneuralnetwork processing architecture, including amultilayer perceptron and a competitive neural network, is used to classify defects using the output amplitude of the eddy-current probe (ECP) and its operation frequency. The crack detection, classification and estimation of the geometrical characteristics, for different classes of defects, are described in the paper.