['Chemoradiotherapy (CRT) is currently performed for patients with advanced esophageal carcinoma. Sensitivity of tumours to CRT differs from one case to another and may be influenced by the expression of biological molecules. The aim of this study was to identify biological markers which could predict sensitivities of esophageal squamous cell carcinoma (ESCC) to CRT.', 'A total of 84 patients with stage I-IV ESCC were evaluated. The cytokeratin 19 fragment antigen 21-1 (CYFRA21-1) and carcinoembryonic antigen (CEA) levels were measured before CRT by enzyme-linked immunosorbent assays in patients with primary ESCCs using 3.4 ng ml(-1) and 3.3 ng ml(-1), respectively, as cut-off values. The relationships between pretreatment expression of CYFRA 21-1 and CEA and the effectiveness of CRT were analysed.', 'The complete response (CR) rates of the primary tumours estimated by computed tomography in patients with high levels of CYFRA21-1 and CEA were 10% (3/30) and 4.2% (1/24), while in cases with low CYFRA21-1 and CEA the CR rates were 50% (27/54) and 48.3% (29/60), respectively (p = 0.002 and 0.003). The effective rates (CR+PR) in CYFRA21-1 high and low groups were 60% (18/30) and 96.3% (52/54), while in CEA high and low groups they were 58.3% (14/24) and 93.3% (56/60), respectively (p = 0.013 and 0.013).'] Are cYFRA21-1 and CEA useful markers for predicting the sensitivity to chemoradiotherapy of esophageal squamous cell carcinoma?