Purpose: To investigate whether phosphatidylcholine (PPC) has a protective effect on mucosa-irradiated rats. Methods: The rats were orally fed with 25, 50, and 100 mg PPC/kg body weight (b.w.), respectively, for 3 weeks before irradiation. After administering the medication and 1 day after irradiation, a 20 cm segment of the proximal jejunum was perfused in situ and peptidase activities, as well as the concentrations of the membrane components, were assayed. Results: We have shown that the application of a low dose of 25 mg PPC/kg b.w. daily for 21 days can prevent damage to membranes induced by 2.0 Gy as represented in the peptidase release profiles during the perfusion of the proximal jejunum of rats. Higher dose levels did not increase the protective effect. Conclusions: These findings suggest that a low dosage of exogenous PPC is capable of hindering the impairment of membranes induced by a small dose of radiation.