Results are provided for a study of the slag resistance of periclase-carbon specimens based on modified phenol formaldehyde resin using different forms of filler, i.e., sintered and fuzed periclase. It is established that penetration of molten slag and its reaction with refractory is independent of the form of periclase filler. There is a reduction in slag penetration into refractory with introduction of modifying additions.In recent years interest in MgO-C-refractories has increased due to there high thermal shock resistance and slag corrosion resistance. Introduction of carbon into periclase refractories improves a number of operating properties [1]; there is a marked change in elasticity modulus, thermal conductivity and depth of slag penetration into an object. However, a disadvantage of these refractories is oxidation of the carbon contained within them [2], and antioxidants are used in order to increase oxidation resistance and mechanical strength [3 -5].Magnesium strongly affects the state of the oxide-carbon contact both during carbonization of a binder, and also at high temperature [6]. Therefore the more dense the periclase powder, the higher is object strength [7]. Use of a porous filler reduces ultimate strength in compression after carbonization, which is connected with additional oxidation of phenol formaldehyde binder by oxygen, absorbed by the porous surface of periclase powder, and therefore in order to produce high quality periclase-carbon refractories and retain a stable structure of coke residue, dense fuzed periclase powder is used [7]. Use of densely sintered periclase filler under stable uniform conditions points to higher strength properties [8,9]. However, the strength of periclase-carbon refractories is markedly affected not only by the form of periclase used, but also by the binder.Technology has been developed [10 -12] for the production of unfired periclase-carbon refractories based on modified phenol formaldehyde resin with high strength indices and the possibility has been demonstrated of using sintered periclase instead of fuzed material. From the multitude of physical and chemical actions, which lead to a change in composition and structure of periclase-carbon refractories, the most intense breakdown is caused by reaction with molten slag. Therefore it is proposed to increase the specifications for slag resistance and resistance to cracking for these objects.Slag resistance of periclase-carbon specimens manufactures according to technology developed in [11,13], using different forms of periclase as a filler, is studied in this work. The composition of specimens is provided in Table 1.In order to determine slag resistance by the crucible method a blind hole was drilled over the center in test specimens with a diameter of 8 mm and depth of 13.5 mm into which basic slag was poured. Slag composition, %: SiO 2 38.63, Al 2 O 3 7.54, CaO 46.84, MgO 4.46, MnO 0.31, FeO 0.37, S 1.85; CaO/SiO 2 = 1.21. Specimens were heat treated at 1400°C (soaking for 2 h, rate of temperature increase 300°...