To investigate the anti-tumor effect of Chinese medicine Gecko on human esophageal carcinoma cell lines and xenografted sarcoma 180 in Kunming mice and its mechanism. The serum pharmacological method was used in vitro. The growth rates of the human esophageal carcinoma cells (EC9706 or EC1) were measured by a modified 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The transplanted tumor model of the mouse S180 sarcoma was established. Fifty mice were randomly divided into five groups (n=10). Three Gecko groups were treated respectively with oral administration of Gecko powder at a daily dose of 13.5 g/kg, 9 g/kg, and 4.5 g/kg. The negative group (NS group) was treated with oral administration of an equal volume of saline and the positive group (CTX group) was treated with 100 mg/kg Cytoxan by intraperitoneal injection at the first day. After 2 wk of treatment, the anti-tumor activity was evaluated by tumor tissue weighing. The impact on immune organ was detected based on the thymus index, spleen index, phagocytic rate and phagocytic index. The protein expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) were detected by immunohistochemistry. The cell apoptotic rate was detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay. The OD value in each group treated with Gecko after 72 h was reduced significantly in EC9706 and in EC1. The tumor weight in each group of Gecko was decreased significantly (1.087+/-0.249 vs 2.167+/-0.592; 1.021+/-0.288 vs 2.167+/-0.592; 1.234+/-0.331 vs 2.167+/-0.592; P<0.01, respectively). However, the thymus index and Spleen index of mice in Gecko groups had no significant difference compared with the NS group. The immunoreactive score of VEGF and bFGF protein expression of each Gecko group by immunohistochemical staining were lowered significantly. The apoptosis index (AI) of each group was increased progressively with increase of dose of Gecko by TUNEL. Gecko has anti-tumor effects in vitro and in vivo; induction of tumor cell apoptosis and the down-regulation of protein expression of VEGF and bFGF may be contributed to anti-tumor effects of Gecko.