The uptake of taurocholate (TC) by the perfused rat liver was studied by the multiple indicator dilution technique using single injections of 14-C-labeled TC and 99m-Tc-labeled albumin. For determination of the intra- and extravascular space, 51-Cr-labeled erythrocytes and albumin were used. TC was found to be distributed into an extravascular space equivalent to that of albumin. Analysis of the dilution curves, according to Goresky (Am J Physiol 207:13-26, 1964), revealed that the initial TC uptake rate increased with increasingly TC dose in a nonlinear fashion, exhibiting saturation kinetics which obeyed the Michaelis-Menten equation. The initial maximal uptake rats (Vmax) was found to be 32.5 nmoles per s and g of liver, a value exceeding the maximal steady state capacity (Tm) for excretion of TC into the bile. The half-saturation constant (Km) was 90.6 nmoles per g of liver, indicating that this system is operating far from saturation at physiological levels of bile acids in portal blood.