In the present work, we report a direct precipitation of nanocrystalline powders of alkaline-earth hydroxyapatites of the compositions, A(10)(PO4)(6)(OH)(2) (A = Ca, Sr or Ba) from aqueous solutions containing Na3PO4 and MCl2 (M = Ca, Sr or Ba) at 150 degrees C for 2 days and autogeneous pressure under hydrothermal conditions. The products were characterized by X-ray powder diffraction, transmission electron microscopy and scanning electron microscopy. The paper also discusses a convenient and economical hydrothermal route for the extraction of nanocrystalline calcium hydroxyapatite, from fish bone waste. (c) 2006 Springer Science + Business Media, Inc.