Bile and pancreatic juice contain a number of parameters for cancer chemoprevention. Indole-3-carbinol (I3C) and phenethyl isothiocyanate (PEITC), which are hydrolytic products of brassica plants, have been established to be anti-cancer agents. Here, we developed a method for the continuous and selective sampling of bile and pancreatic juice, and the effects of I3C and PEITC on bile and pancreatic excretion and γ-glutamyl transpeptidase (γ-GTP) activity in the samples were investigated. Male Fisher 344 rats (eight weeks of age) were challenged intragastrically with I3C (150 mg/kg) or PEITC (160 mg/kg) for five days. Twenty-four hours after the final administration, cannulation was undertaken into the rats' bile and pancreatic ducts, and the bile and pancreatic juice were separately collected for 48 h. In this rat model, bile was stably excreted, and the bile and pancreatic excretion of the control rats was 21.9 ± 1.4 ml/48 h and 12.8 ± 1.7 ml/48 h, respectively. Bile excretion for the first 24 h significantly increased in the I3C- or PEITC-treated rats compared with the control rats. In the case of pancreatic juice, excretion during the first 24 h significantly increased in the PEITC-treated rats. In bile, γ-GTP activity was significantly increased for the first 24 h in the I3C- and PEITC-treated rats, but no difference was observed in the pancreatic juice. Increases of bile excretion and γ-GTP activity in bile might be a factor involved in the anti-cancer effect of I3C and PEITC. Our rat model described here is a useful tool for the study of cancer chemoprevention.