Objective To identify effects of bile acids on pancreatic cancer, The ultrastructure and growth of PANC-1 and MIA PaCa-2 cell lines in crude bile modified medium were studied. Methods The growth of PANC-1 and MIA PaCa-2 cells in RPMI 1640 with or without 1％, 2％ and 4％ of the purified crude bile (containing total bile acids 10.17mmol/L) was assessed for 2, 4, 6, 8d by using MTT assay to determine inhibitory rate. The cell surface and intracellular ultrastructure of PANC-1 cells was investigated by SEM and TEM at 24h and 48h, respectively. Re sults The proliferation of both cell lines in bile treated medium were greatly retarded (P ＜0.001). The inhibitory rate of 1％, 2％ and 4％ bile on Panc-1 cells in 4d were 38％, 60％ and 66％, respectively (P ＜0. 05), on MIA PaCa-2 cells at 4d were 28％, 39％ and 52％, respectively (P ＜0. 05). The cells grown in bile for 48h lost their mi crovilli, their mitochondria and other organelles became vacuolated. Conclusion The bile acids in bile has cytotoxicity on PANC-1 and MIAPACA-2 cells, which may inhibit pancreatic cancer progress in patients clinically.