The purpose of the study was to evaluate the clinical significance of the intensity of metallothionein (MT-I/II) expression and its relationship to two different proliferation markers, Ki-67 antigen and minichromosome maintaince 2 protein (MCM-2) in 117 patients with invasive ductal breast carcinoma (IDC). A significantly higher MT-I/II expression was noted in the grade 3 (G3) carcinomas as compared to those of G1 and G2. A positive correlation was observed between the MT-I/II expression and both proliferation markers, Ki-67 (r=0.20, p=0.0343) and MCM-2 (r=0.25, p=0.0065). Also a strong positive correlation was noted between Ki-67 and MCM-2 expression (r=0.52, p<0.0001). No significant correlations were found between the analyzed markers and tumour size, lymph node metastasis, oestrogen expression (ER), progesterone receptor (PR) or human epidermal growth-factor receptor (HER-2) expression. Out of the three studied markers only the high expression of Ki-67 exhibited a negative impact on patient overall and event free survival and was an independent prognostic factor. MT-I/II and MCM-2 protein expression was not correlated with poor patient outcome, although MCM-2 expression correlated (Fisher's exact test) positively with grade of malignancy (p=0.0018) and negatively with ER (p=0.0002) and PR (p=0.0056) expression. To conclude, MT-I/II may play a key role in IDC proliferation, but is not a useful prognostic factor of this disease.