It is unclear whether neutral steroids and bile acids are involved in large bowel carcinogenesis. This study was conducted to compare the concentration of these faecal constituents at the different stages of the adenoma-carcinoma sequence. Neutral sterols and free bile acid concentrations were determined from stool samples collected form patients with large bowel cancer (n= 47), large adenoma ≥1 cm (n= 42), small adenoma (n= 24), and controls (n= 104). The distribution of tertiles between cases and controls was analysed using odds ratio (OR), with 95% confidence interval (CI), comparing (two-sided tests) the second tertile (OR2) and the third tertile (OR3) to the first one. Persistence of primary bile acids appeared as a protective factor against cancer: (OR = 0.09, 95% CI 0.02–0.54). High values of cholesterol were associated with cancer risk (OR2= 5.8, 95% CI 1.3–26.6; OR36.4, 95% CI 1.3–31.4). High values of cholesterol were more frequently observed in patients with large adenomas than in controls (OR2= 8.5, 95% CI 1.9–37.5; OR3= 4.3, 95% CI 0.9–20.9). Neutral sterols, cholesterol especially, may play a role in adenoma growth and adenoma transformation into carcinoma. Persistence of primary bile acids may afford protection.