The clinical significance of the promoter methylation of the NDRG1 gene was determined by investigating the relationship between NDRG1 methylation and the clinicopathological characteristics of breast cancer patients, such as menopause, tumor grade, TNM stage, lymph node metastasis, p53 mutation, tumor size, HER2 status, and the Ki67 proliferation index. The gene discussed is NDRG1; the disease is breast cancer.