Transcriptional inactivation of breast cancer gene 1 (BRCA1) by DNA methylation is a frequent event in sporadic breast cancers. To investigate whether BRCA1 methylation is associated with survival in Chinese patients with sporadic breast cancer, BRCA1 methylation was determined using methylation specific PCR in 536 sporadic breast cancers. Survival curves for patients with methylated and unmethylated BRCA1 were compared using the log-rank tests. Twenty-six percent (139/536) of patients exhibited BRCA1 methylation in their tumors. The degree of BRCA1 methylation was correlated with clinical stages of breast cancer, but was not significant. Patients with BRCA1 methylated tumors had a significantly worse 5-year disease-free survival (DFS) and 5-year disease-specific survival (DSS) than did patients with unmethylated tumors (DFS: 73.2%vs 82.6%, P = 0.045; DSS 80.5%vs 87%, P = 0.038, two-sided). In conclusions, BRCA1 methylation is a frequent event in breast cancer and is associated with poor clinical outcome in Chinese women with breast cancer.