Bile acid CoA synthetase has been discovered in rat kidney. Incubation of kidney microsomes with [14C]chenodeoxycholic acid and CoA produced a single peak with the high performance liquid chromatography (HPLC) retention time of CDC-CoA. This peak, when incubated with purified bile acid CoA:amino acid N- acyltransferase (BAT) from human liver and either taurine or glycine, led to the formation of CDC-taurine or CDC-glycine, respectively. Kinetic analysis revealed apparent K(m)s for CDC and CoA of 2.5 μM and 2.6 μM, respectively. This activity appeared specific for bile acids as it was not inhibited by benzoic acid or salicylic acid, known substrates for other rat kidney CoA synthetases. This demonstrates that the kidney has the potential for bile acid metabolism and may have a role in bile acid physiology.