Effects of hydrogen enrichment and steam addition on laminar burning velocity of methane-air premixed flame were studied both experimentally and numerically. Measurements were carried out using the slot burner method at 1 bar for fresh gases temperatures of 27 degrees C and 57 degrees C and for variable equivalence ratios going from 0.8 to 1.2. The hydrogen content in the fuel was varied from 0% to 30% in volume and the steam content in the air was varied from 0 to 112 g/kg (0-100% of relative humidity). Numerical calculations were performed using the COSILAB code with the GRI-Mech 3.0 mechanism for one-dimensional premixed flames. The calculations were implemented first at room temperature and pressure and then extended to higher temperatures (up to 917 K) and pressures (up to 50 bar). Measurements of laminar burning velocities of methane-hydrogen-air and methane-air-steam agree with the GRI-Mech calculations and previous measurements from literature obtained by different methods. Results show that enrichment by hydrogen increases of the laminar burning velocity and the adiabatic flame temperature. The addition of steam to a methane-air mixture noticeably decreases the burning velocity and the adiabatic flame temperature. Modeling shows that isentropic compression of fresh gases leads to the increase of laminar burning velocity. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.