Tensile and flexural creep tests of 20 vol % SiC Whiskers reinforced Si3N4 composite processed by gas pressure sintering have been carried out in air in the temperature range of 1000-1300 degrees C. The stress exponent for flexural creep is 16 at 1000 degrees C. However, at 1200 and 1250 degrees C the stress exponents for both tensile and flexural creep vary with increasing stress. In the low stress region, the activation energy for creep is 1000 kJ/mol. In the high stress region, it is 680 kJ/mol. The different creep mechanisms dominate in the low and high stress regions, respectively.