The role of Th17 and Treg cells in esophageal squamous cell carcinoma (ESCC) remains unknown. This study aims to investigate the imbalance between Th17 and Treg cells in patients with early ESCC and its significance. Flow cytometry was performed to determine the percentage of Th17 and Treg cells in the peripheral blood of ESCC patients, and immunohistochemistry was utilized to detect the expression of forkhead box protein 3 (FOXP3(+)) and interleukin (IL)-17 in the tissue specimens from 30 patients with early ESCC and 30 normal human controls. The proportion of Th17 and Treg cells in peripheral blood of the ESCC patients was 1.34 +/- 0.30% and 3.03 +/- 1.13%, respectively, and in the normal controls the values were 0.52 +/- 0.18% and 1.97 +/- 0.92%, respectively. These differences were statistically significant (P<0.05). The Th17/Treg ratio in the ESCC patients was higher than in the normal control group (0.50 +/- 0.20 and 0.31 +/- 0.13, respectively, P<0.05). Compared with the peri-tumoral tissues and the tumor-free esophageal tissues, the fresh tumor tissues showed significantly higher expression of IL-17 (163.64 +/- 53.9, 98.19 +/- 25.27 and 44.10 +/- 17.86, respectively, P<0.01), and FOXP3(+) cells (115.45 +/- 31.74, 92.73 +/- 16.19 and 69.09 +/- 26.63, respectively, P<0.05). In addition, the ratio of the Th17/Treg cells in the fresh tumor tissues was higher than in the peri-tumoral tissues and the tumor-free esophageal tissues (1.45 +/- 0.45, 1.08 +/- 0.30 and 0.70 +/- 0.30, respectively, P<0.05). In conclusion, the imbalance between the Th17 and Treg cells demonstrated here might play an important role in the pathogenesis of ESCC.