Galvanostatic water electrolysis was conducted in 2 wt % KOH and 0.1 N H2SO4 solutions under microgravity. The corresponding terrestrial experiments employed two kinds of electrode configurations: a vertical cathode and downward-facing horizontal cathode-over-anode (C/A) arrangement. The latter configuration was designed to simulate the microgravity (mu-G) condition. The ohmic resistance of the gas bubble dispersion zone near Pt electrodes was measured by the current interrupter method and compared for these three different cases. The transient variation of resistance for C/A configuration behaved similarly to that under mu-G in H2SO4, but the resistance varied more slowly in KOH. When water electrolysis was conducted with a vertical plane cathode under 1-G, the resistance reached an essentially constant value within a few 100 ms in KOH, whereas the resistance increased linearly for a few seconds, followed by a zig-zag variation in H2SO4. Water electrolysis under mu-G resulted in stable froth layer formation, and the accompanying ohmic resistance increased in linear proportion to the froth layer thickness. The contributions of electrode surface coverage by bubbles and electrolyte-phase bubble void fraction to the ohmic drop were also assessed. These parameters were compared with corresponding values in terrestrial experiments analyzed by Balzer and Vogt. (c) 2006 The Electrochemical Society.