Redox reactions of aqueous chloramphenicol (CPL) solutions with H., e(aq)(-), OH., (CH3)(2)(OH)C*, and CO2(.-) were studied using pulse radiolysis techniques. Rate constants for the reaction of these radicals with CPL were determined. Using MV2+/MV.+ as the standard couple, the one-electron redox potential of the CPL was determined. High-performance liquid chromatography was employed for the investigation of the degradation products. The possible formation of aryl radicals from CPL and nitrosobenzoic acid (one of the several products formed In irradiated CPL aqueous solution) and its subsequent reaction with O-2 can lead to the formation of aryl peroxyl radicals. The reactivity of various p-substituted aryl peroxyl radicals with 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) was studied. Such a reaction product could be responsible for observed side effects of CPL.