Randomised crossover studies in three separate groups of 10 healthy volunteers were undertaken to determine the effects of biliary lipid composition and bile salt metabolism of daily dietary supplementation for four weeks with the purified fibre components pectin (12 g/day), cellulose (15 g/day) and lignin (12 g/day). The subjects' biles were initially unsaturated with cholesterol and no significant changes in the lithogenic indices or mean percentages of cholesterol, phospholipid, or total bile acids after any of the supplements were observed. After pectin, the mean (+/- SD) percentage of cholic acid decreased significantly from 42.8 (+/- 10.8) to 39.0 (+/- 11.2), the mean (+/- SD) percentage of deoxycholic acid increased significantly from 18.2 (+/- 13.7) to 25.4 (+/- 13.5) and C14-deoxycholate metabolites were raised significantly by 65%. After cellulose, the mean (+/- SD) percentage of chenodeoxycholic acid was increased significantly from 33.6 (+/- 6.3) to 35.4 (+/- 7.0), the mean (+/- SD) percentage of deoxycholic acid decreased significantly from 18.6 (+/- 9.6) to 14.2 (+/- 8.3) and C14-deoxycholate metabolites halved. Lignin did not exert any significant effects. Though these results show that individual fibre components are associated with quite different effects on bile acid metabolism, in the short term no significant effect on biliary cholesterol saturation was observed in bile initially unsaturated with cholesterol. The bile acid changes most likely result from the different effects on colonic metabolism induced by the individual fibre components.