A polymer containing bile acid pendant groups was prepared by free-radical polymerization of the 3 alpha-methacrylate derivative of cholic acid. The polymer formed fibrils of about 1 nm in diameter in aqueous media and further assembled into bundles or lamella plates, as observed by transmission electron microscopy. After immersing the fibrils in simulated body fluid with ion concentrations equivalent to those in human plasma, plate-like crystals formed on the surface of the fibril assembly. The diffraction pattern corresponding to the (001) plane of hydroxyapatite was identified by transmission electron microscopy and selected area electron diffraction. The plate-like, single crystal hydroxyapatite formed on such a polymeric assembly may be useful in the matrix design for biomimetic mineralization and in the development of scaffold materials for hard tissue engineering.