This paper describes a numerical and experimental analysis of the optimum loadings of noble metals (Pt, Ir) in electrocatalytic layers of the polymer electrolyte membrane (PEM) water electrolysis cells. Based on the obtained results, the Pt loading of ca. 0.4 mg/cm(2) (or 1 mg/cm(2) of Pt/C with 40 wt. % of Pt) and ca. 2.5 mg/cm(2) of IrO2 loading could be recommended. The developed mathematical model has shown that these optimum values are derived from the interference of activation and ohmic losses in the electrocatalytic layers. The membrane-electrode assembly (MEA) with these noble metal contents does not exhibit significant catalytic layer degradation within 4000 h of operation. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.