The kinetics of the oxidation of hypophosphorous acid by vanadium (V) was investigated. Increase in hydrogen ions, increased the rate of oxidation. The energy of activation, frequency factor and entropy of activation were calculated to be 18.8 ± 0.5 k.cals/mole, (4.4 ± 0.8) 10u (litre mole-1 sec-1) and - 5.3 ± 0.35 (e.u.) respectively. A free radical mechanism for the reaction has been proposed. © 1970, Walter de Gruyter. All rights reserved.