Objectives: To compare the effect of rubbing breast milk versus lanolin in the treatment of symptoms of sore nipples. Methods: We carried out this randomized clinical trial on 225 mothers with sore nipples in the Neonatal Intensive Care Unit of Imam Reza Hospital in Mashhad, Iran from April 2001 for 2 years. We randomly divided the patients into 3 groups. The first group rubbed the hind milk on their nipples at the end of each breast-feeding session, and the second group used lanolin locally on the nipple 3 times a day, and cleaned the nipple with a wet cloth before infant feeding. The third group did not use anything (control group). We corrected the breast-feeding technique of all mothers throughout the study. After the first visit, we reexamined the patient on the third, fifth, seventh and tenth days. We obtained information with interviewing and physical examination by using a questionnaire. We based the sore nipple improvement on absence of irritation according to mothers opinions. We analyzed the obtained information using the SPSS version 11.5 software, and the used tests were Chi-Square test, Mann-Whitney test, and Kruskal-Wallis test. Results: The first group (breast milk users) included 78 patients, the second group (lanolin users) included 74 patients, and the third group (control group) included 73 patients. The 3 groups were similar in gravidity, delivery method, pre-delivery breast feeding education, the beginning time of the first breast feeding, prior success breast feeding experiences, detergent agents usage for nipples, use of formula, and pacifier. Clinical manifestations, such as appearance time of symptoms, irritation and breast wound were not significantly different. The healing time was different in these 3 groups (p=0.038) according to the mean ranking in the groups. The healing time in the lanolin group was longer than the breast milk group (p=0.029) and the control group (p=0.028). No side effects were noted during the study. Conclusion: This study suggests that, due to the better healing of the sore nipple with breast milk, its availability, without payment and side effect, breast milk is recommended for the treatment of sore nipples.