To elucidate urinary bile acid patterns in patients with biliary atresia (BA), 15 sulfated and nonsulfated bile acids in urine were separately measured by high-performance liquid chromatography. This relatively simple technique for fluorescence detection utilizes the enzyme 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) to reveal urinary bile acid patterns. By this method, recovery rates of sulfated and nonsulfated bile acids in urine were satisfactory, and this analysis was shown to be applicable to clinical situations. In 10 patients with BA, the mean level of total bile acids in urine (23.35 +/- 18.51 mumol/day) was seven times higher than the mean level in eight normal infants (3.05 +/- 2.05 mumol/day). In the infants with BA, the mean level of total sulfated bile acids was about half of the total bile acid level. The main components of urinary nonsulfated bile acids in BA were glycocholic acid (6.21 +/- 5.55 mumol/day) and taurocholic acid (2.28 +/- 1.33 mumol/day), whereas the main components of the urinary sulfated bile acids were glycochenodeoxycholic acid (4.58 +/- 6.97 mumol/day) and taurochenodeoxycholic acid (3.67 +/- 3.54 mumol/day). Chenodeoxycholic acid, which is relatively toxic to the liver, may more easily be conjugated with sulfate and, hence, excreted into urine at a faster rate than cholic acid. Marked individual variations in urinary bile acid patterns were observed not only in BA patients but also in normal controls.