Abstract: Porous desiccant material, such as silica gel, activated alumina, molecular sieves or mixtures thereof, is efficiently regenerated for reuse as a drying agent by irradiating a bed of the desiccant material with microwave energy preferably having a frequency of from 2400 MHz to 2500 MHz or from 900 to 915 MHz to heat and substantially affect only moisture adsorbed by the material and to vaporize the moisture in consequence of the heating of the moisture, the vaporized moisture being purged out of the bed with a forced draft of scavenging air while the bed undergoes irradiation by the microwave energy, and the resulting mixture of scavenging air and vapor being disposed of by discharging the mixture to an effluent receiving region isolated from the bed.