We have investigated the pair tunneling process inYBa2Cu3O7−xstep-edge Josephson junctions by studying the lifetime of the metastable zero-voltage state determined by the thermal activation out of the potential well. The junctions have a hysteretic current–voltage characteristic at 4.2 K, which allows the recording of transitions and switching distribution from the Josephson current to the resistive state. By applying an external magnetic field, we have found a strong dependence of the activation energy on the field intensity. Striking similarities with analogous measurements performed on lowTcconventional tunnel junctions suggest that the highTccounterparts can be described by a standard model for long junctions. ©1998 American Institute of Physics.