The aim of the present study was to determine the role of interleukin-6 (IL-6) in the epithelial-mesenchymal transition (EMT) of human intrahepatic biliary epithelial cell (HIBEC) lines in vitro. HIBECs were stimulated with IL-6 at concentrations of 0, 10, 20, 50 and 100 µg/l for 24 h. A wound healing and Transwell assay were performed to determine the migratory and invasive capacity of HIBECs, respectively. Following 24 h of incubation, IL-6 at 10 and 20 µg/l significantly increased the number of migrated and invaded cells (P<0.05), while stimulation with 50 and 100 µg/l IL-6 resulted in a further increase of the migratory and invasive capacity compared to that in all other groups (P<0.05). Furthermore, reverse-transcription quantitative polymerase chain reaction and western blot analyses were used to detect the mRNA and protein expression of EMT markers E-cadherin and vimentin in HIBECs. Decreased mRNA levels of E-cadherin accompanied by higher mRNA levels of vimentin were observed in the 10, 20, 50, 100 µg/l IL-6 groups compared to those in the 0 µg/l group (all P<0.05). Furthermore, the protein expression of E-cadherin was decreased, while that of vimentin was increased in the 50 and 100 µg/l IL-6 groups compared to those in the 0, 10 and 20 µg/l IL-6 groups (all P<0.05). The present study therefore indicated that IL-6 promoted the process of EMT in HIBECs as characterized by increased migration and invasion of HIBECs and the typical changes in mRNA and protein expression of the EMT markers E-cadherin and vimentin.