The clinical significance of free cancer cells in pleural lavage fluid detected by molecular methods during surgery remains uncertain in esophageal squamous cell cancer (ESCC). We therefore evaluated the relationship between free cancer cells and clinicopathological findings, and compared the reverse transcriptase-polymerase chain reaction (RT-PCR) method with conventional cytological examination. Pleural lavage fluid from 38 consecutive patients was obtained at two time points; immediately after thoracotomy and before thorax closure. Papanicolaou and Giemsa staining as well as carcinoembryonic antigen (CEA)-specific RT-PCR were performed. The positivity rates obtained using cytological examination and CEA-mRNA expression were 5.3 and 15.8%, respectively. Positive results were observed in pleural lavage fluid after tumor resection. No significant differences in clinicopathologic factors were seen, irrespective of CEA-mRNA expression status. Among the 5 patients exhibiting CEA-mRNA positivity, 2 experienced hematogenous recurrence, 2 experienced mixed recurrence and 1 experienced pleural dissemination. With regard to mode of recurrence and mean period between surgery and relapse, no significant differences were seen between CEA-mRNA-positive and CEA-mRNA-negative patients. Although disease recurred in almost all patients exhibiting CEA-mRNA expression, due to the relatively small sample in the present study the clinical significance must be investigated further in a larger number of patients.