Because of its excellent thermal, mechanical and electrical properties silicon carbide is widely used for heating elements. Nevertheless these elements are affected by electrical ageing (increase of electrical resistivity during use). This phenomenon is generally attributed to oxidation but no satisfactory answer has been presently found to reduce its effects. The aim of this study is to obtain a better understanding of the degradation of the electrical properties through the oxidation behavior of hot pressed samples containing various amount of additives. Eight dense SiC ceramic samples with Al2O3, AlN, Y2O3 and NiO additives were prepared by hot pressing. The influence of these additives on sintering, oxidation behavior and electrical properties was evaluated. Formation of an yttrium garnet phase leads to liquid phase sintering but decreases the oxidation resistance. The dependence of electrical resistivity with temperature can be explained by the presence or not of a metallic phase formed between Ni and Si. This secondary phase permits a low (< 5 Omega . cm) and almost constant value of the electrical resistivity from ambient temperature up to 950 degreesC to be obtained.