The growth rate of the hydroxyapatite (0001) face in pseudophysiological solution was measured directly for the first time by Moire phase shift interferometry. Common-path-type interferometry and a newly developed signal processor used for the phase shift technique enabled the precise and stable measurement of growth rates. It was determined that the growth rate was strongly time-dependent. The growth rate gradually decreased with time and finally ceased although the concentration of the solution remained constant. The thickness of the layer grown on the seed crystal was about 500-700 nm, while the growth rate during initial growth stages was of the order of 10(-2) nm/s. respectively. Detailed surface morphology was observed by atomic force microscopy (AFM), indicating that the growth mode was multiple two-dimensional nucleation.