The kinetics of the reactions of OH with acetic acid, acetic acid-d(3) and acetic acid-d(4) were studied from 2 to 5 Torr and 263-373 K using a discharge flow system with resonance fluorescence detection of the OH radical. The measured rate constants at 300 K for the reaction of OH with acetic acid and acetic acid-d4 (CD3C(O)OD) were (7.42 +/- 0.12) X 10(-13) and (1.09 +/- 0.18) X 10(-13) cm(3) molecule(-1) s(-1) respectively, and the rate constant for the reaction of OH with acetic acid-d(3) (CD3C(O)OH) was (7.79 +/- 0.16) X 10(-13) cm(3) molecule(-1) s(-1). These results suggest that the primary mechanism for this reaction involves abstraction of the acidic hydrogen. Theoretical calculations of the kinetic isotope effect as a function of temperature are in good agreement with the experimental measurements using a mechanism involving the abstraction of the acidic hydrogen through a hydrogen-bonded complex. The rate constants for the OH + acetic acid and OH + acetic acid-d(4) reactions display a negative temperature dependence described by the Arrhenius equations k(H)(T) = (2.52 +/-1.22) X 10(-14) exp((1010 +/- 150)/ T) and k(D)(T) = (4.62 +/- 1.33) X 10(-16) exp((1640 +/- 160)/ T) cm(3) molecule(-1) s(-1) for acetic acid and acetic acid-d(4), respectively, consistent with recent measurements that suggest that the lifetime of acetic acid at the low temperatures of the upper troposphere is shorter than previously believed.