Non-sulfated bile acid levels including cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA), ursodeoxycholic acid (UDCA), five taurine conjugates, and five glycine conjugates in duodenal juice were measured in 50 Chinese infants with cholestasis to test their diagnostic value. All 17 with biliary atresia (BA) cases, 11 out of 26 neonatal hepatitis (NH) cases and one case with paucity of the interlobular bile duct were without detectable bile acids. In those NH patients with detectable bile acids, the major components were conjugated forms of CA and CDCA, which was similar to all 6 cases of the comparison group with other diseases. The minor bile acid components identified in them were glycine conjugated UDCA, free CDCA, free CA, and free and conjugated DCA. Only one patient with NH had taurine conjugated LCA. The mean total duodenal bile acid level in 15 patients with NH was significantly lower than that in the 6 patients of the comparison group. Most patients with NH had a CDCA/CA ratio of less than one, indicating that cholic acid is the predominant form in their bile. Glycine conjugated bile acids were the predominant bile acids present in 11 out of 15 patients with NH and 4 out of 6 of the comparison group patients. The results suggest that the detection of duodenal bile acids by a sensitive HPLC method is of limited value in making a differential diagnosis between BA and NH.(ABSTRACT TRUNCATED AT 250 WORDS)