A catalytic effect of non-ionic (tween-80) micelles on the rate of oxidation of thiaminehydrochloride (vitamin B-1) and pyridoxine hydrochloride (vitamin B-6) by sodium salt of p-toluene sulphonamide (chloramine-T) in acidic medium has been observed and rate has been found to be proportional to {k' + k" [Tween-80]}, where k' and k" arc the rate constants in absence and in presence of surfactant, respectively. The rate showed a first order, a fractional order and a zero order dependence on [Chloramine-T](0), [Vitamin](0) and [H+](0), respectively. The association/binding between the oxidant and the surfactant micelle is supported by the spectrophotometric evidence. A mechanism has been proposed and binding parameters have been evaluated.