Rate coefficients for H + O-2 -> OH + O (R-1) and H + O-2 + M -> HO2 + M (R-9) were measured via OH absorption behind reflected shock waves, being: k(1) = 6.73 x 10(15) T-0.50 exp(-8390 K/T) cm(3) mol(-1) s(-1) at T = 950-3100K and k(9,0)/[Ar] = 5.55 x 10(18) T-1.15 cm(6) mol(-2) s(-1) at T = 950-1200 K. Our experimental results for k(1) strongly support recent ab initio calculations showing temperature curvature due to back dissociation, HO2 -> O + OH following O + OH -> HO2 if the reaction is considered from the reverse direction. Published by Elsevier B.V.