The rate constant of the disproportionation channel la of the self-reaction of hydroxyl radicals OH + OH -> H2O + O (1a) was measured at ambient temperature as well as over an extended temperature range to resolve the discrepancy between the IUPAC recommended value (k(1a) = 1.48 x 10(-12) cm(3) molecule(-1) s(-1), discharge flow system, Bedjanian et al. J. Phys. Chem. A 1999, 103, 7017) and a factor of ca. 1.8 higher value by pulsed laser photolysis (2.7 x 10(-12) cm(3) molecule(-1) s(-1), Bahng et al. J. Phys. Chem. A 2007, 111, 3850, and 2.52 x 10(-12) cm(3) molecule(-1) s(-1), Altinay et al. J. Phys. Chem. A 2014, 118, 38). To resolve this discrepancy, the rate constant of the title reaction was remeasured in three laboratories using two different experimental techniques, namely, laser-pulsed photolysis-transient UV absorption and fast discharge flow system coupled with mass spectrometry. Two different precursors were used to generate OH radicals in the laser-pulsed photolysis experiments. The experiments confirmed the low value of the rate constant at ambient temperature (k(1a) = (1.4 +/- 0.2) X 10(-12) cm(3) molecule(-1) s(-1) at 295 K) as well as the V-shaped temperature dependence, negative at low temperatures and positive at high temperatures, with a turning point at 427 K: k(1a) = 8.38 X 10(-14 )x (T/300)(1.99) x exp(855/T) cm(3) molecule(-1) s(-1) (220-950 K). Recommended expression over the 220-2384 K temperature range: k(1a) = 2.68 X 10(-14) x (T/300)(2.75) x exp(1165/T) cm(3) molecule(-1) s(-1) (220-2384 K).