The kinetics of the reactions of hydroxyl radical with n-undecane (n-C11H24) and n-dodecane (n-C12H26) has been studied at 240-340 K and a total pressure of 1 Torr using the relative rate/discharge flow/mass spectrometry (RR/DF/MS) technique. The rate constants at 298 K for these reactions were determined to be k(n-undecane+OH) = (1.59 +/- 0.24) 10(-11) cm(3) molecule(-1) s(-1) and k(n-dodecane+OH) = (1.83 +/- 0.26) x 10(-11) cm(3) molecule(-1) s(-1), respectively. The rate constants of these reactions were found to positively dependent on temperature at 277-340 K, and negatively dependent on temperature at 240-277 K. The atmospheric lifetime of these compounds are estimated to be 25.8 and 19.8 h for n-undecane and n-dodecane, respectively, based the kinetics results in the present study.