The interaction between bovine serum albumin (BSA) and sodium taurodeoxycholate (NaTDC), a component of the bile in mammals, have been investigated in a wide range of experimental conditions and for several protein to surfactant ratios. The solution region has been investigated by surface tension sigma, freezing point depression DeltaT, as well as by integral heat of dilution data DeltaH(i.dil). The corresponding properties of NaTDC in aqueous solutions have been investigated too. Surfactant binding onto the protein is presumably controlled by a delicate balance of hydrophobic and electrostatic contributions, responsible for the adduct stability, but does not give rise to precipitation or coacervate formation. This behaviour is in line with current knowledge on the solution behaviour of BSA-TDC complexes occurring in hepatic and gallbladder bile. (C) 2004 Elsevier B.V. All rights reserved.