Transparent hydroxyapatite (HAP) was prepared by sintering gel-cast powder compacts at 1000degreesC for 2 h; the resultant HAP material was studied using X-ray diffractometry, transmission electron microscopy, scanning electron microscopy, and microhardness measurement. Nanoscale HAP crystallites were prepared using a precipitation method that involved calcium nitrate and ammonium dihydrogen orthophosphate solutions; the preparation was conducted at a temperature of 0degreesC. The precipitate was gel-cast and sintered at 1000degreesC in the form of a transparent ceramic that had a uniform grain size of 250 mum. The maximum Vickers microhardness obtained for a sample sintered at 1000degreesC was 6.57 GPa. The sintering behavior of gel-cast samples prepared from high-temperature-precipitated HAP was compared with that of material prepared at 0degreesC.