SiCf-SiBC composites were produced using NLM 202 and Hi-Nicalon SiCf fibers. Tensile creep tests were performed under a reduced pressure of argon. These composites show a good creep resistance at 1473 K with a strain rate ranging from 10(-9) to 10(-7) s(-1), depending on the stress level. The creep strength was improved by using Hi-Nicalon instead of NLM 202 SiCf fibers, to the extent of increasing the loadability by 50 MPa at the same operating temperature or increasing the temperature by 50 K for the same load. The damage observed in SEM micrographs and the use of the damage mechanics provide evidence that creep is governed by a damage-creep mechanism in two steps.