In recent years quite some research has been carried out in microwave-assisted catalysis and in microwave-assisted catalyst synthesis. Presently we have tested the use of dielectric fields for in situ reactivation of passivated Ni-on-alumina using dielectric fields. As a model catalytic reaction, hydrogenation of toluene was employed. The reaction itself was studied using both dielectric and conventional heating, thereby assessing the impact of dielectric heating on catalyst structure and activity. Further, we have studied the application of a dielectric field to regenerate Ni-on-alumina deactivated by coke formation. It is shown that in situ activation of a passivated catalyst in a dielectric field is indeed possible, but in situ decoking is not likely to be feasible, because for moderate electric field strengths the temperatures attained by coke particles are insufficient to realize carbon methanation.