The rate of oxidation of ClO2- by HOBr is first-order in each reactant and is general-acid assisted in the presence of phosphate or carbonate buffers. The products are ClO2 and ClO3-, where the relative yield depends on the concentration ratio of ClO2-/OH-. The kinetic dependence indicates the presence of a steady-state intermediate, HOBrOClO- (or HOBrClO2-), that undergoes general acid-assisted reactions to generate a metastable intermediate, BrOClO (or BrClO2). This intermediate reacts very rapidly by two competing pathways : in one path ClO2- reacts to form 2ClO(2) and Br-, and in the other path OH-(or H2O) reacts to form ClO3- and Br-. Competition between these pathways determines the yield of ClO2 but does not affect the rate of loss of HOBr. The reactions are followed by the formation of ClO2 in the presence of excess ClO2-. The rate expression for the loss of HOBr is k(1)[ClO2-][HOBr]Sigma(k(HA)[HA])/(k(-1) + Sigma(k(HA)[HA])), where k(1) (for the formation of the intermediate) is 97 M-1 s(-1) and k(HA)/k(-1) (M-1) values, which depend on the acid (HA) strength, are 3.1 x 10(5) for H3O+, 8.3 for H2PO4-, and 0.064 for HCO3- (25.0 degrees C, mu = 1.0 M). Reactions between HOBr and ClO2- are much faster than those between HOCl and ClO2-.