Various p-4H-SiC(0001) substrates such as on-axis, 8degrees off-axis, and 8degrees off-axis with epitaxial layer have been characterized by ESR both before and after oxidation. In SiO2/p-4H-SiC, several ESR signals which have the line positions varying with the angle between the magnetic field and the crystal axis of the substrate have been found. In SiO2/p-6H-SiC, EPR parameters for the new center (denoted as PERC-1) having a dangling bond character have been determined.