Objective To study the clinical and prognostic value of CK19 mRNA-positive circulating tumor cells in early breast cancer patients. Methods We analyzed the peripheral blood in 50 patients with early breast cancer after surgery and before the initiation of any adjuvant treatment for the presence of CK19 mRNA-positive circulating tumor cells using a nest reverse polymerase chain reaction assay. All patients were followed up. Results CK19 mRNA-positive cells were detected in 40.0 %(20/50) of patients with early breast cancer, 12.5 %(3/24) of patients with breast benign lesions, but 5 %(1/20) in healthy individuals (P =0.017,P =0.004); 11 to 20 of them relapsed during the follow-up period (P =0.002). There was no significant association between the detection of CK19 mRNA-positive cell and the patients' menstrual status, tumor stage, tumor size, etc (P ＞0.05). Detection of peripheral-blood CK19 mRNA-positive cells was associated with reduced median relapse-free interval in early breast cancer patients (P =0.007). Conclusion CK19 mRNA is one of the molecular markers for the detection of circulating tumor cells in early breast cancer. Detection of peripheral blood CK19 mRNA-positive cells might be an important predictive value as a marker of relapse in early breast cancer patients.