Epidemiological investigations have shown an association between the incidence of colonic cancer, dietary habits, and bile acid metabolism. We analyzed the fecal bile acid excretion pattern in 23 patients with colonic carcinoma and in 21 controls. We determined the total bile acid concentration, the concentration of individual bile acids as a measure for bacterial degradation, and the degree of sulfation. Separation of nonsulfated and sulfated bile acids was achieved by the lipophilic anion-exchanger DEAP-Sephadex-LH 20, quantification of individual bile acids by gas-liquid chromatography. Corresponding with a significantly lower stool mass per day, colonic cancer patients had a lower daily bile acid excretion. But we found no statistically significant difference between the groups in the fecal concentration of total or individual bile acids or their mode of conjugation. There was a wide variation of total bile acid concentration within each group. Most bile acids were expectedly in the free state, only a low percentage in the glycine- or taurine-conjugated form. The sulfated fraction was small and not different in the two groups. Although our data do not refute the hypothesis of bile acids being implicated in the pathogenesis of colorectal cancer, they do not support it.