This paper presents a study of CH4/Air/H-2/O-2 premixed laminar flames using a ratio of H-2/O-2 equal to 2/1. This gas mixture represents the products of the electrolysis of water. To date, only numerical analysis has been carried out on these kinds of blends and using H-2/O-2 percentages of only up to 10% by volume. Furthermore, there have been no reports of experimental analysis or possible flame instabilities associated with the enrichment of the mix with H-2/O-2. In this study, the effect of adding water electrolysis products on the laminar burning velocity and stability of lean premixed methane/air flames is studied for different percentages of H-2/O-2 (10 and 25) in the lean combustion regime, which is relevant for most engineering applications. The results show that a higher addition of H-2/O-2 to methane increases the laminar burning velocity. In particular, at Phi = 0.75, intrinsic instabilities are observed for mixtures with 25% of H-2/O-2 in methane. With the addition of H-2/O-2, the laminar flame thickness decreases and the growth rate increases. Hence, the addition of H-2/O-2 to a premixed natural gas flame enhances the hydrodynamic instabilities. (C) 2016 Elsevier Ltd. All rights reserved.