The effect of saponins isolated from soya bean flour on the incidence of aberrant crypt foci (ACF) induced by azoxymethane (AOM) in the colonic wall of CF1 mice was investigated. Four weekly injections of AOM, a known colon carcinogen, were administered to mice. One week after the last injection, mice were placed on an AIN-76 diet supplemented with 3% soya bean saponins or continued on the basal AIN-76 diet. Another group of mice was placed on the saponin diet without AOM initiation to observe the effect of saponins on the growth characteristics of mice. Dietary intake of soya saponins significantly reduced the incidence of ACF at the end of 14 weeks (postinitiation). Noninitiated mice maintained on a similar soya bean saponin-supplemented diet did not show any adverse effects on the growth and overall health of the animals. These findings suggest that soya bean saponins can play an important role in inhibiting the incidence of ACF in the colon of mice.