Pt/Ti/WSi/Ni ohmic contacts to n-SiC, initially annealed at 950 and 1000 °C for 30 s, were evaluated for thermal stability via pulsed/cyclic thermal fatigue and aging experiments at 650 °C. Modifications of material properties in response to cyclic thermal fatigue and aging tests were quantitatively assessed via current–voltage measurements, field emission scanning microscopy, atomic force microscopy, and Rutherford backscattering spectrometry. Negligible changes in the electrical properties, microstructure, and surface morphology/roughness were observed for both annealed ohmic contacts in response to 100 cycles of acute cyclic thermal fatigue. Aging of the 950 °C annealed contact for 75 h at 650 °C resulted in electrical failure and chemical interdiffusion/reaction between the contact and SiC substrate. The 1000 °C annealed contact retained ohmicity after 100 h of aging and was found to be chemically and microstructurally stable. These findings indicate that the 1000 °C annealed Pt/Ti/WSi/Ni ohmic contact to n-SiC is thermally stable and merits strong potential for utilization in high temperature and pulsed power devices. © 2002 American Institute of Physics.