Genetic alterations in the p53 tumor suppressor gene with or without protein overexpression have been reported to be associated with sporadic breast cancer. To assess the role of p53 in infiltrative ductal breast carcinoma among Iranian patients, p53 protein expression and p53 gene mutations were studied by immunohistochemical analysis and single-strand conformation polymorphism, respectively. The p53 protein was expressed in 25 out of 51 (49%) tumors and p53 gene mutations were detected in 17 out of 37 (46%) tested tumors. No significant correlation was observed between p53 gene mutations and p53 protein expression. There was no significant correlation between p53 abnormalities (mutation and expression) and tumor size, histological grade, nodal status, and progesterone receptor expression. However, a non-statistically significant trend of association (P=0.07) was observed between p53 gene mutations and lack of estrogen receptor. The high percentage of alterations both in p53 gene and protein among southern Iranian breast cancer patients suggests that p53 is probably one of the genes involved in sporadic breast cancer in this area.