We studied the effects of oral taurine supplementation on bile acids conjugation and duodenal bile salt concentrations in infants. Seventeen infants receiving enteral artificial nutrition were investigated. At the beginning of the study they were 6 to 14 weeks old, in good nutritional state, without malabsorption, protein-losing enteropathy and liver or infectious diseases. After at least 8 days of a stable, taurine-free regimen the infants received oral taurine supplementation (36-45 micromol/kg.24 h) for 8 days. Bile acids were measured before and after each supplementation period in bile samples obtained by duodenal tubing, using enzymatic methods and colorimetry. According to the initial plasma taurine levels before supplementation, the infants were divided into two groups: I) plasma taurine levels less than 60 mumol/l (mean 47 +/-5 mumol/l, n = 8); II) plasma taurine levels greater than 70 mumol/l (mean 77 +/- 2 mumol/l, = 9). After 8 days of taurine supplementation a significant increase of plasma and urinary taurine (P less than 0.01),total duodenal bile salt concentrations (P less than 0.05), total duodenal tauroconjugates (P less than 0.05),taurocholate (P less than 0.01), taurochenodeoxycholate (P less than 0.05), and glycocholate (P less than 0.01), duodenal concentrations, and a significant decrease of the glycoconjugate/tauroconjugate ratio (P less than 0.05), were observed, but only in group I. in group II infants we only noted a significant increase of urinary taurine (P less than 0.01), and of duodenal total tauroconjugates (P less than 0.05). This study shows that the biliary effects of an oral taurine supplementation depends on taurine status and that in taurine-depleted infants intakes of exogenous taurine higher than 45 mumol/kg. 24 h are perhaps necessary for optimal bile salt effects.