The p53 gene is a tumour suppressor gene that encodes a 393-amino-acid nuclear DNA-binding phosphoprotein. The significance of p53 detection is that p53 mutation is linked with chemo-resistance and transformation to more aggressive disease in a large number of tumour types and it was confirmed that mutant p53 is involved in neoplastic transformations. In addition, the expression of p53 has been closely correlated with clinicopathological findings. Since breast cancer has been reported as one of the most frequent malignancies in women in Malaysia, the expression of p53 was studied in 382 cases of invasive ductal carcinoma of the breast, obtained from three major hospitals in the North East States of Malaysia. The study utilized an enzyme immunohistochemistry assay for the detection of p53. It was found that p53 was expressed in 29.6% of all the study cases. Furthermore, its expression was significantly correlated with the age and the clinical grading of the disease. No significant statistical correlations were depicted with lymph node status, tumour size, side of tumour, and expression of estrogen and progesterone receptors. Nevertheless, knowledge of the p53 status may be valuable in making clinical decisions regarding diagnosis, prognosis and therapy.