One gram of dehydrocholic acid was injected intravenously into two patients with percutaneous transhepatic cholangial drainage, and the biotransformed metabolites profiles over a 120-min period in serum and bile were analyzed. In serum unconjugated 3 alpha-hydroxy-7,12-dioxo-cholanoic acid (3 alpha-OH-7,12-OXO) acid was markedly increased after the injection of dehydrocholic acid, and reached about 80 microM within 30 min. On the other hand, conjugated 3 alpha, 7 alpha-dihydroxy-12-oxo-cholanoic acid (3 alpha,7 alpha-OH-12-OXO) was consecutively increased with lag time to an elevation of 3 alpha-OH-7,12-OXO. In bile, the major constituent of metabolites was conjugated 3 alpha,7 alpha-OH-12-OXO (more than 90% of the excreted metabolites), while conjugated 3 alpha-OH-7,12-OXO was detected as minor constituent. Therefore, between bile and serum, there was great difference in biotransformed metabolites profiles. The mechanism of elevation of unconjugated 3 alpha-OH-7,12-OXO in serum remains obscure, but this new finding raised a question as to whether organ-reducing 3-keto group of dehydrocholic acid is restricted to the liver.