The impact of dilution on laminar burning speed of two different fuels (methane and isooctane) is studied. In the present study, three different diluents are used--nitrogen, carbon dioxide, and a mixture representative of exhaust gases issued from a stoichiometric combustion of methane. Experimental results and PREMIX computations of the CHEMKIN package, using two different kinetic schemes, are presented and compared with literature results, when available. Initial pressure and temperature conditions are respectively 0.1 MPa and 300 K. For both fuels, a larger decrease of the laminar burning speed is obtained for carbon dioxide dilution than for nitrogen dilution. This observation is directly linked to the increase in heat capacity of the dilution gas but also to the carbon dioxide dissociation, even if the heat capacity effect seems to be predominant.