Foil specimens of DIN 1.4914 martensitic stainless steel were irradiated with 6.2 MeV protons at temperatures from 673 to 810 K and tensile stresses up to 480 MPa. During the test, strain rates were determined alternately with and without irradiation. Irradiation at dose rates up to 4x10-6 dpa/s did not alter the creep rates compared to thermal creep. Stress changes caused transient strains which were of similar magnitude under irradiation and under thermal creep. The creep rates can be described by an exponential stress dependence with a temperature dependent exponential factor and by an exponential temperature dependence vith an activation energy of about 3.0 eV. The creep rates are compared to literature data for materials of similar composition. This comparison shows a strong dependence of creep strength of this material on small compositional variations. It further indicates a lower stress dependence of the creep rate under varying stresses compared to results of constant stress experiments.