A feeding experiment was conducted to examine the e¡ect of a supplemental ethanol extract from a defatted soybean meal on the biliary bile status and intestinal conditions of rainbow trout Oncorhynchus mykiss. A semi-puri¢ed control diet based on casein (Cont) and three diets supplemented with the extract (ES), bovine bile salts (BS) and their combination (ESBS) were fed to trout (10 g) for 6 weeks. The growth, feed e⁄ciency ratio, fat digestibility and gallbladderand hepato-somatic indices of ¢sh fed diet ES decreased. Compared with this group, these parameters were improved in ¢sh fed diet ESBS. The total biliary bile salt content was the lowest in ¢sh fed diet ES and this group had a high proportion of chenodeoxycholyltaurine. The inclusion of the bile salts to diet ES (diet ESBS) increased the total biliary bile salt content. A similar trend was observed in the bile salt concentration of intestinal digesta. Although morphological changes occurred in epithelial cells of the distal intestine of ¢sh fed diet ES, the histological features of ¢sh fed diet ESBS were similar to those of ¢sh fed diet Cont. These results indicate that alcohol-soluble substances of soybean meal cause physiological changes in the biliary bile and intestine of rainbow trout.