The effects of rat bile-pancreatic juice (BPJ) on Fe^<2+> induced oxidation of soybean phosphatidylcholine (PC) was monitored to investigate the influence of this digestive juice on oxidative damage in the gastrointestinal tract. A large volume of BPJ (50% in the suspension of PC, v/v) suppressed the lipid peroxidation, but a smaller volume had the reverse effect. BPJ could decompose free fatty acid hydroperoxides (FFA-OOH) at a lower concentration (〜0.2mM) completely, although its phospholipase activity liberated FFA-OOH from PC hydroperoxides. Sodium deoxycholate enhanced the Fe^<2+> induced oxidation of PC in a concentration-dependent manner when PC was suspended in the buffer. Boiled BPJ suppressed Fe^<2+> induced and peroxyl radical initiated oxidation of sodium deoxycholate micelles of soybean PC up to 〜50% (v/v). It was strongly suggested that rat BPJ had a biphasic effect on Fe^<2+> induced oxidation of phospholipids depending on the enhancement by bile salts and the inhibition by antioxidant components with radical-scavenging activity and hydroperoxide-decomposing activity.