Mice were fed low-fibre, or that supplemented with soluble fibre (konjac glucomannan, KGM; inulin), or insoluble fibre (cellulose) to determine how these three fibres modulated the acute colonic responses to an azoxymethane (AOM) treatment. Results indicated that KGM and inulin exerted greater anti-genotoxic effects compared to cellulose and up-regulated the gene expressions of glutathione S-transferase and antioxidant enzymes. The apoptotic index in the distal colon was the greatest and the expression of Bcl-2 was the lowest in the KGM group 24h after the AOM treatment. On the other hand, the proliferative index and expression of Cyclin D1 were lower in all fibre groups. Furthermore, KGM increased cecal short-chain fatty acid contents, and both KGM and inulin increased fecal probiotic concentrations. This study suggested that soluble fibres were more effective than cellulose on ameliorating AOM-induced genotoxicity by up-regulating antioxidant enzyme genes, and enhancing epithelium apoptosis by down-regulating Bcl-2.