Studies of bile salt structure using nuclear magnetic resonance (NMR) and X-ray crystallography have suggested that micellar association of bile salts is a function of side chain length and of packing of the side chain and the steroid nucleus. Lanthanide NMR probe analysis has been used to determine the structure of what is probably the monomer of the bile salt glycocholate. These approaches to the structural chemistry of bile salt intra- and intermolecular interactions are providing the basis for the design of artificial bile salt-like compounds for use in the study and treatment of human gallstone disease.