The laminar flame speeds of dimethyl ether (DME)/air mixtures at room temperature and atmospheric pressure were determined experimentally over an extensive range of equivalence ratios, with and without 15% nitrogen dilution, using particle image velocimetry and a stagnation flame burner configuration. The laminar flame speeds were determined by linear extrapolation of the measured reference flame speed versus stretch rate to zero stretch rate. Experimental results are compared with available literature data and predictions of the model based on the recently published detailed reaction mechanism of DME oxidation. The measured values are significantly larger at all equivalence ratios than the values recently reported from spherical bomb experiments. A comparison of laminar flame speed calculations using a DME oxidation mechanism developed earlier in our laboratory agrees reasonably well with the present experimental data, without modifications. Differences from prior calculations using this mechanism reported by Daly et al. are resolved to be a result of differences in numerical constraints rather in than kinetics or transport databases. Modifications of the mechanism suggested by Daly et al. are not compatible with DME validation results in the original mechanism development or with flame speed predictions for other simple fuels such as methane. (C) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.