The serum levels of soluble interleukin 2 receptor (sIL-2R) before and after radiotherapy in 57 esophageal carcinoma patients and 20 healthy controls were determined with an enzyme-linked immunosorbent assay. The objectives of this study were to determine the value of serum SIL-2R level as an index of tumor burden, and its predictive value in response to therapy and prognosis. The data showed that the serum sIL-2R level in esophageal carcinoma patients was significantly higher than that of healthy controls (P < 0.001). The elevated serum sIL-2R levels correlated with the length of the esophageal cancer. The serum levels of sIL-2R were significantly reduced at the end of radiotherapy (P < 0.001). Moreover, the serum level after radiotherapy was not different from that of healthy controls (P > 0.05). But, the reduced levels were not related to the immediate response to radiotherapy. These results seem to suggest that monitoring serum sIL-2R levels has clinical and prognostic significance in patients with esophageal carcinoma.