Rate consts. for the disproportionation reaction OH + OH -> HiO + O in the range 250-580 K were measured by flash photolyzing H2O/N2 mixts. and monitoring the decay of OH by using quant. UV resonance spectrometry. The result (k1 = (3.2 +- 0.8) 10-12 exp(-242/T) cm3 mol-1 s-1 does not correlate with existing high temp. data and confirms previously suggested non-Arrhenius behavior for this reaction. On the basis of all available data, the temp. variation of k1 over the range 250-2000 K is best represented by the empirical expression k1(T) = exp(-27.73 +- 1.49 * 10-3T) cm3 mol-1 s-1. The extent of the Arrhenius graph curvature can be reconciled by a \"close-collision\" model incorporating the energy variation of accessible product states.