The physics of a gas diffusion electrode-membrane cell is discussed and comparisons are made with experimental data. In particular, a second order expansion has been used to correlate the maximum current density data, valid for both small to large overpotentials and electrode specific surface areas. It is also demonstrated that the limiting or maximum current density for the diffusion limit can be predicted by assuming simple molecular diffusion across the membrane and the ion reference (open circuit) concentration in the cathode. An expression is also developed to account for differences in reactant gas concentrations and flowrates between reference and normal operating conditions. Comparisons are made between the theory and maximum current data for the absorption of H2S, CO2 and SO2. These comparisons suggest that the current density limitations of the cell are affected by electrochemical reaction rates on the cathode surface. Other possible limitations for electrochemical cell performance are discussed.