The binary phase equilibria for the system sodium taurodeoxycholate-water have been studied. The system forms a liquid crystalline phase in addition to the previously known isotropic solution phase at 22 degrees C. H-2 (water) NMR quadrupole splitting, SAXS data in combination with the polarizing microscopic texture observed for the liquid crystal indicate that the liquid crystalline phase consists of a hexagonal-type aggregate structure. A metastable liquid crystal, probably with lamellar-type structure, also appears to exist prior to the formation of the stable hexagonal phase. A micellar growth is measured with the NMR self-diffusion method for the isotropic solution phase. Electrical conductance experiments are used to determine the liquid crystal-solution thermal transition.