The clinical implications of bone marrow micrometastases (BMM) detected by RT-PCR in esophageal squamous cell carcinoma (ESCC) have not been elucidated. We evaluated the relation between the presence of BMM, both before and after surgery, and clinicopathologic findings in patients with ESCC. Bone marrow samples from 48 patients with ESCC were obtained from the iliac crest before and after surgery. After total RNA was extracted from each bone marrow sample, carcinoembryonic antigen (CEA)-specific RT-PCR was performed. BMM was detected by RT-PCR in 10 of the 48 patients. Four patients each had positive signals only before or only after surgery and 2 patients had positive signals both before and after surgery. There were no significant differences in clinicopathologic factors, including neoadjuvant therapy, between patients with BMM and without BMM. To date, the rates of recurrent disease in patients with BMM and without BMM are 80% (8/10) and 50% (19/38), respectively, a difference which is not significant. The 4-year survival rates of patients with BMM and without BMM are 10.0% and 47.3%, respectively. Recurrence and survival rates were poorer in patients with RT-PCR positivity, although the differences were not significant. A larger study is required to clarify the clinical impact of BMM.