Simultaneous heat and mass transfer in periodic-flow heat and mass exchangers, or regenerators, with hygroscopic matrix materials has been analyzed. The coupled heat and mass transfer equations are derived for boundary-layer controlled heat and mass transfer and include longitudinal heat conduction in the matrix. A numerical method of the finite-difference type is applied to the steady-state performance. Results for a water vapor-air mixture show the influence of matrix heat and moisture capacities on temperature and humidity efficiencies. Distributions of air temperature, air humidity, matrix temperature and adsorbent moisture content are calculated in drying as well as recovery operations.