A detailed reaction mechanism of n-heptane combustion has been elaborated and validated by comparison of computed mole fraction profiles with those measured in four premixed flames stabilized on a flat-flame burner under low pressure )6 kPa). in a wide range of equivalence ratios (0.7 - 2.0). As the MBMS technique was used for species analyses, both stable and active species were considered. The predictions of the model are in good agreement with the experimental results for most stable species. The main active species H. OH and O are fairly well predicted in rich flames while disagreements are observed in the lean and the stoichiometric flames. The intermediate radicals can be grouped in three classes depending on the accuracy of the model predictions: (i) good agreement in Ihe whole range of equivalence ratios, (ii) predicted mole fractions differing from the experimental values by a constant factor in the four flames studied, (iii) difference between computed and measured maximum mole fractions differing from lean to rich flames. In the discussion of the results, the observed disagreements between the model and the experiments have been generally interpreted in term of experimental inaccuracies. However, the modeling of the combustion chemistry for heavy fuel molecules has been carried out so far on the basis of experimental data referring only to stable species and the problems faced with intermediate radicals can result from experimental uncertainties but also from deficiencies in the mechanism or inaccuracies in the kinetic data.