The kinetics of the reaction OH + NH3 have been studied by means of the flash photolysis/laser-induced fluorescence technique. The rate of this reaction was investigated in the range 273-433 K under more extensive conditions (68 < P/Torr < 504, 0.29 < [NH3]/1015 molecules cm-3 < 36.1) than previously. The results from experiments with the Xe lamp and with the KrF laser for photolysis agree well within the experimental uncertainties, indicating the absence of interference due to excess NH2 which was produced by photolysis with the Xe lamp. A fit of rate coefficients to the Arrhenius equation yields k = (3.29 ± 1.02) × 10-12 exp[-(922 ± 100)/T] cm3 molecule-1 s-1, with k = (1.47 ± 0.07) × 10-13 cm3 molecule-1 s-1 at 297 K; the uncertainties represent one standard error. The rate constant of the interfering reaction, OH + NH2 → products, was also estimated to be less than 7 × 10-12 cm3 molecule-1 s-1.