This paper deals with the methodology used in a COST 517 research concerning study of inclusions in high alloyed steel for mechanical purpose. In order to establish in a quantitative and statistically justifiable way the relationship between impurities, inclusions and mechanical properties of high alloyed steels, we have to insure that the microstructure on the whole batch of specimens of the same origin is similar. This required appropriated heat treatments before achieving mechanical tests. Otherwise, metallurgical properties of the samples could vary, and the relationship between inclusions and mechanical properties misunderstood. Regardless of the melting or die atmosphere during the melting, inclusions are present in varying amounts in every commercial steel products. Since inclusions significantly influence properties and behavior of materials and at the same time give indications on the quality of the steel, it is quite interesting to precise their nature and their origin. This requires methods of identifying the inclusions and a knowledge of the history during steel making.