Abstract: A gas chromatographic method for the determination of radiolytic degradation products in the HDEHP-TBP-nC12H26 system is described. The degradation products are phosphoric acid, mono-and di-butyl phosphoric acid and mono-(2-ethylhexyl) phosphoric acid. The acidic components were analyzed with a "p" model detector after being converted to methyl esters by diazomethane. The separation column was a stainless steel column (φ 3×2000mm) packed with 1% 1,4-butanediol succinate on 102 kieselguhr (60-80 mesh). The tripropyl phosphate was used as internal standard and the peak was measured by peak height method. The results showed that four degradation products could be rapidly determined with a standard deviation of±10% in five minutes.