Abstract. The aim of this paper is to present an expert system for identification of the basic reinforcement concrete structures parameters like: rebars diameter, thickness of a concrete cover and a kind of rebar's alloy (class). The results of measurement carried out by the eddy current transducers were utilized for the designed system. Measured waveforms are represented by two kinds of attributes, the d-factors represent a waveform shape, and a maximal amplitude. In order to extract an association rules between the specific attributes and the structure parameters a rough set theory was used.