We have investigated mRNA and protein expression of TWIST, Vimentin and E-cadherin in ESCC (oesophageal squamous cell carcinoma) and explored their relationship with tumour's infiltration and metastasis. RT-PCR (reverse transcriptase-PCR) was used to evaluate mRNA expression of TWIST, E-cadherin and Vimentin in 40 cases of ESCC. The protein expression of the genes was examined by immunohistochemical staining in each specimen. Expression of TWIST, E-cadherin and Vimentin mRNA and protein with clinicopathologic parameters were analysed. mRNAs of TWIST, Vimentin and E-cadherin were expressed in 75, 55 and 35% respectively of ESCC, i.e. significantly different from that in normal oesophageal mucosa (15, 0 and 85% respectively; P<0.01). In ESCC with LN (lymph node) metastasis, expression of TWIST and Vimentin mRNA, but not E-cadherin mRNA was significantly higher (100 and 83%) than in ESCC without LN metastasis (64 and 43%, P=0.018) respectively. Levels of mRNA expression of the 3 genes followed similar patterns to their above-mentioned frequencies. Protein expression of TWIST, E-cadherin and Vimentin were observed in 70, 35 and 50% respectively of ESCC, which were significantly different from normal mucosa (15, 80 and 0%; P<0.001). In ESCC with LN metastasis, protein expression of TWIST and Vimentin, but not E-cadherin, were significantly higher (100 and 75%) than in ESCC without LN metastasis (61 and 39%). Protein expression of TWIST was positively correlated with Vimentin (r=0.327, P=0.039), but negatively correlated with E-cadherin (r= -0.633, P=0.000). Thus, both mRNAs and proteins of TWIST and Vimentin were significantly overexpressed in ESCC, especially ESCC with LN metastasis. The mRNA and protein of E-cadherin were down-regulated in ESCC. These results suggest potential roles of TWIST as the promoter of tumour invasion and metastasis associated with down-regulation of E-cadherin.