Faecal bile acids (FBA) have been implicated in colon carcinogenesis. The results of case-control studies of colorectal cancer and polyp patients are, however, conflicting. The aim of this study was to examine the influence of faecal bile acids on occurrence, growth and recurrence of colorectal polyps, and to see if a mixture of calcium and antioxidants might possibly act on cancer precursors through the effect on FBA. A total of 116 polyp-bearing patients were recruited from the outpatients department. Polyps < 10 mm in diameter were left in situ and measured by annual colonoscopy for 3 years. The patients received placebo or a mixture of antioxidants and calcium carbonate, 1.6 g calcium ion daily. Faecal samples were collected annually; the first, 1 month after start of intervention, freeze dried and subjected to bile acid profile analysis. Two age and sex matched control groups were recruited (n = 35), one from healthy volunteers (healthy controls) and one from the outpatients referred for colonoscopy, with no polyps (hospital controls). Twelve of 47 patients from the healthy volunteers had polyps (healthy polyp patients). One or more adenomas were found in 93 patients. The faeces of the hospital controls had significantly higher concentrations of total and secondary bile acids than did the healthy controls. There was no difference in FBA profile between the polyp group and the hospital controls, but significantly higher concentration of total and secondary faecal bile acids in the healthy polyp patients compared with the healthy control group (P < 0.05). No increased concentration of FBA were found in the polyp patients with multiple polyps (n = 21) or previous treatment for colorectal cancer (n = 7). No associations between FBA profile and growth or recurrence of colorectal polyps were found. The polyp patients receiving active medication had higher faecal concentrations of total and secondary bile acids in the beginning of the study than at the end, in spite of a good compliance. The present study does not support bile acids as being important markers of initiation or growth of small and medium sized colorectal adenomas. In the present study the calcium and antioxidants did not seem to affect the growth or recurrence of colorectal adenomas by increased TBA excretion in the faeces.