Highly　pure　brushite　(CaHPO4.　2H(2)O)　coatings　on　porous　Ti6Al4V　substrates　were　prepared　by　electrodeposition　from　aqueous　electrolytes.　The　influence　of　hydrothermal　treatment　parameters　on　brushite-to-hydroxyapatite　conversion　and　the　morphology　and　phase　composition　of　hydroxyapatite　(HAP)　coatings　was　studied.　It　was　found　that　the　content,　Ca/P　atomic　ratio,　grain　size　and　pore　size　of　HAP　in　coatings　increase　with　increasing　hydrothermal　treatment　temperature,　and　that　increasing　the　pH　value　can　promote　brushite-to-HAP　conversion　and　reduce　the　grain　size　of　HAP.　Under　optimal　conditions,　highly　pure　HAP　coatings　with　needle-like　crystals　and　non-stoichiometric　form,　which　are　similar　to　those　of　calcium　phosphate　in　human　bone,　can　be　obtained.　(C)　1999　Kluwer　Academic　Publishers.