A number of existing mathematical models of heat- and mass-transfer processes taking place inside a material undergoing vacuum freeze-drying are reviewed in brief. Some physical considerations with respect to freeze-drying in a vacuum are presented and a corresponding mathematical model is proposed to describe coupled heat and mass transfer inside the material undergoing freeze-drying. The model is based on linear nonequilibrium thermodynamic results. After appropriate numerical analysis, the model is expected to yield new data to be utilized in vacuum freeze-drying design and technology.