A conjugate heat and mass transfer model was developed for microwave freeze drying within porous media with dielectric cores. The set of transient governing equations developed was solved numerically using finite volume method with variable time-steps. Analysis of numerical results may lead to following main conclusions: (I) by carefully choosing the loss factor and size of the dielectric cores could dramatically reduce the drying time, (2) the size and the loss factor epsilon" of the dielectric core are the two important parameters influencing the drying process, (3) there may be two sublimation fronts in existence within the porous media. (C) 2004 Elsevier Ltd. All rights reserved.