Reactions at gas-diffusion electrodes are modeled by treating the electrolyte meniscus geometry as a wedge. The resulting differential equations are solved analytically for the constant-overpotential case and numerically for all forms of polarization. The model's prediction agrees with experimental data for hydrogen oxidation on platinum in sulfuric acid. The effects of various physical parameters contributing to concentration, ohmic, and activation polarization are considered. The contact angle and the three-phase contact line have not been adequately addressed in previous studies and are shown to be very important parameters. This suggests a new approach in modeling conventional gas-diffusion electrode performance. NOMENCLATURE dissolved gaseous reactant concentration (mol me3) solubility of the reactant gas (mol m-r) current (A) number of electrons transferred in the rate-limiting step total number of electrons transferred per molecule of reactant overpotential (V) overpotential at the tip of the meniscus (V) transfer coefficient Faraday constant (Coul mol-') Ideal gas constant( Jmol-' K-') temperature (K) width of the meniscus wedge (length of contact line) (m) length of the meniscus wedge (m) wetted electrode area (m') cross-sectional area of the meniscus (m2) conductance of the electrolyte (ohm r m ') exchange current density (A m *) differential pressure (N m-r) surface tension of the electrolyte (N m-') contact angle wedge angle local cone angle pore diameter at the three-phase contact line (m) digusion coethcient (m2 s-r) molecular weight of gas impingement rate of gaseous molecules (mol m -'s-') density of gas (kgmm3)