An experimental investigation of freeze-drying of coffee extract is presented. Effects of freezing rate, concentration and pressure on the drying rate are determined and the results compared with a theoretical model, which expresses the drying rate in terms of the effective diffusivity of the material. The effective diffusivity of the coffee extract was found to be in the range of 20∼60 cm²/sec for slush freezing, 20∼40 cm²/sec for slow freezing, and 5∼16 cm²/sec for fast freezing. The mechanism of water vapor transport appeared to be mainly the bulk diffusion in the slow or slush freezing, and the Knudsen diffusion in the fast freezing.