Cadmium is a known human lung carcinogen, although some studies indicate a link between cadmium exposure and human breast cancer. The objective of this study was to assess cadmium concentration in breast tissue samples of patients with breast cancer and benign breast tumor. MATERIAL AND METHODS. The concentration of cadmium was determined in breast tissue samples of 21 breast cancer and 19 benign tumor patients. Two samples of breast tissue from each patient, i.e. tumor and normal tissue close to tumor, were taken for the analysis. Cadmium was determined by atomic absorption spectrometry (Perkin-Elmer, Zeeman 3030). RESULTS. In patients with breast cancer, the mean cadmium concentration was 33.1 ng/g (95% CI, 21.9-44.4) in malignant breast tissue and 10.4 ng/g (95% CI, 5.6-15.2) in normal breast tissue (P=0.002). In patients with benign tumor, the corresponding values were 17.5 ng/g (95% CI, 8.4-26.5) and 11.8 ng/g (95% CI, 5.1-18.5) (P=0.3144). There was a statistically significant difference in cadmium concentration between malignant and benign breast tissues (P=0.009). CONCLUSION. The data obtained show that cadmium concentration is significantly higher in malignant breast tissue as compared with normal breast tissue of the same women or benign breast tissue. Further studies are necessary to determine the association between cadmium concentration in malignant breast tissue and estrogen receptor level, and smoking.