The kinetics of reactions of OH radical with n‐heptane and n‐hexane over a temperature range of 240–340K has been investigated using the relative rate combined with discharge flow/mass spectrometry (RR/DF/MS) technique. The rate constant for the reaction of OH radical with n‐heptane was measured with both n‐octane and n‐nonane as references. At 298K, these rate constants were determined to be k1, octane = (6.68 ± 0.48) × 10−12 cm3 molecule−1 s−1 and k1, nonane = (6.64 ± 1.36) × 10−12 cm3 molecule−1 s−1, respectively, which are in very good agreement with the literature values. The rate constant for reaction of n‐hexane with the OH radical was determined to be k2 = (4.95 ± 0.40) × 10−12 cm3 molecule−1 s−1 at 298K using n‐heptane as a reference. The Arrhenius expression for these chemical reactions have been determined to be k1, octane = (2.25 ± 0.21) × 10−11 exp[(−293 ± 37)/T] and k2 = (2.43 ± 0.52) × 10−11 exp[(−481.2 ± 60)/T], respectively. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 489–497, 2011