The sensitivity of a depolarized SO2 electrolyzer to various operating parameters has been investigated through numerical modeling. A simplified kinetic expression was first derived to relate the anodic overpotential to both temperature and sulfuric acid concentration. This model allows the cell voltage variation with these two parameters to be studied. The effect of the two-phase parameters associated with hydrogen bubble production was then investigated. Parameters such as electrolyzer orientation, forced convection flow and bubble size were considered. Finally, an overall SO2 balance equation was derived to estimate the sensitivity Of SO2 crossover to the operating conditions. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.