The radiolytic decomposition of tributyl phosphate has been show by burr to product gases, acids, and polymers. the acids that are formed can limit the usefulness of tributyl phosphate for the processing of radioactive materials. The study of acid formation on radiolysis therefor becomes important to us for the understanding of the mechanism of acid formation, the influence of added materials and the effect of the structure of organo- phosphorous compounds. Samples of purified esters have been irradiated in the ORNL cobalt source. Conclusions: (1) The formation of acid from tributyl phosphate during irradiation with cobalt gamma rays involves a mechanism that is not a primary step. Evidence has been obtained for a secondary reaction that is minimized by the presence of certain compounds. (2) Toluene acting as an inhibitor for radiolytic formation of acid may indicate the usefulness of an aromatic hydrocarbon diluent in processing. (3) The aromatic hydrocarbon, when phenyl, was not effective when it was part of the molecule. (4) First tests revealed that dibutyl butyl-phosphonate produced less acid the TBP and may warrant further consideration for process application.