Objective To evaluate the feasibility in early diagnosis, predicting therapeutic effect, recurrence monitoring by examining promoter hypermethylation for cancer-associated genes E-cadherin in cancer tissue and peripheral blood of breast cancer patients. Methods The tumor tissue, paracancer- tissue and the paired plasma were examined for aberrant methylation of E-cadherin gene by methylation-specific PCR in 42 cases of breast cancer and 10 cases of breast benign diseases. Results The incidence of promoter hypermethylation of E-cadherin in tumor tissues was 52.4% and the paired plasma were 33.3%. E-cadherin hypermethylation in plasma samples and tumor samples significantly correlated with each other ( P