The drying kinetics (maximum drying rate, drying constants) and center temperature of selected powder (aspirin, paracetamol, lactose, and maize starch)–solvent (water, ethanol, methanol, and acetone) systems were monitored during microwave-vacuum drying. An experimental microwave-vacuum system (650 W and 2.45 GHz) operated at 61–81 kPa was used. The drying rate profile did not vary with the powder–solvent system; an initial warming-up period was followed by a constant-rate stage and two falling-rate periods. However, the drying kinetics were found to be both powder and solvent dependent, with the drying times for acetone-, ethanol-, and methanol-wetted materials being considerably shorter (up to 89.8%) than those of samples containing water. Although the general form of the temperature profile (short warming-up period, constant-rate stage, and decreasing temperature phase) was similar for all systems, the maximum temperatures varied quite significantly with solvent type, ranging from highest to lowest in the order water-ethanol-methanol-acetone. For most powder–solvent systems, reduced operating pressure facilitated increased drying rates and thus shorter drying times. [ABSTRACT FROM AUTHOR]