The internal stress, σi, and the effective-stress exponent of the dislocation velocity,m*, have been determined during creep of Fe-3.5 at. pct Mo alloy at 1123 K under 10.8 to 39.2 MN/m2 and of Ni-10.3 at. pct W alloy at 1173 K under 19.6 to 88.2 MN/m2. Both alloys have been classified among class I alloys under a certain condition including the present one, because the applied-stress exponent of the steady-state creep rates,n, is almost 3. Values of σi obtained by stress-transient dip test were small and almost independent of the applied stress, σc, in Fe-3.5 Mo alloy. On the other hand, in Ni-10.3 W alloy σi increased with increasing σc as in the case of many pure metals. The value ofm* obtained by analyzing stress-relaxation curves immediately after creep deformation was unity in Fe-3.5 Mo alloy, whereas in Ni-10.3 W alloy it was about 2.5. These results indicate that the rate-controlling mechanisms in creep are different from each other in these two alloys and that the classification according ton-value does not always coincide with the classification according to the rate-controlling mechanisms. It is concluded that the fact thatn ≃ 3 is not a sufficient evidence supporting that creep is controlled by one of microcreep mechanisms.