The dynamical behavior of mass transfer at vertically oscillating surfaces is investigated both experimentally and analytically. The presence of small oscillatory component superimposed on a large steady one that does not reach zero during reversal times was explained in terms of the interaction between a "quasi-steady oscillatory" mechanism near the leading edge of the active mass transfer area, and a "steady diffusive" one far from it. A model was developed that predicted both the time average mass transfer rates, and the time dependent oscillatory component with accuracy being highest at large L/a ratios. Based on the analysis, the model can be used for describing mass transfer at vertically oscillating flat surfaces, and for modeling of systems where knowledge of the mass transfer dynamical behavior is of interest. For cases where only the time average mass transfer rate is required, the contribution of the oscillatory motion to the mass transfer enhancement at vertical surfaces can be estimated adequately using mixed "forced-natural" convections correlation, with the forced convection component estimated based on the time average vibrational Reynolds number of the vibrating surface Re-v = awL/v. (C) 2004 Elsevier B.V. All rights reserved.