Faecal bile acid excretion and intestinal transit time were studied in 18 children with inflammatory bowel disease in clinical remission and with normal stools: 16 with ulcerative colitis, two with Crohn's colitis, mean age 14 years (range 10-17 years). Five healthy children, mean age 12.4 years (range 10-17 years), were studied as control subjects. Most patients were taking sulphasalazine, but none were taking steroids. Transit time was determined by carmine and did not differ between groups. Faeces were collected for 72 hours, and faecal water was prepared by centrifugation of faeces at 15,000 x g for two hours. Bile acids in total faeces and faecal water were studied using capillary gas-liquid chromatography-mass spectrometry. Faecal excretion of total bile acids, unconjugated bile acids, and glycine and taurine conjugates were significantly increased in patients as was faecal water excretion of total bile acids, particularly the taurine conjugates and cholic and chenodeoxycholic acids. Total concentrations of bile acids in faeces and faecal water were two to five times higher in patients. The children with inflammatory bowel disease in clinical remission had high excretion and concentration rates of bile acids, especially taurine conjugates, in both total faeces and faecal water, a finding of considerable interest in the pathogenesis of malignancy in these diseases.