Rod-like calcium hydroxyapatites (Hap) with micrometer size were produced by supplying Ca(CH 3 COO) 2 and NH 4 H 2 PO 4 solutions into a CH 3 COONH 4 solution by varying their feeding rate at 85+/-5 o C and pH 7.4+/-0.2 under nitrogen atmosphere and vigorously stirring. The size of the Hap particles was increased with increase in feeding time (t F ) of the solutions; with increase in the t F the mean particle width and lengths were increased from 0.02 to 0.47 μm and from 0.12 to 5.21 μm, respectively. All these particles were highly crystallized and exhibited a single crystal and Ca-deficient natures with Ca/P atomic ratios of 1.50-1.59. TG and chemical analyses indicated that the chemical composition of the particles can be expressed to Ca 1 0 - x - y (HPO 4 ) x (PO 4 ) 6 - x (OH) 2 - x - 2 y . nH 2 O. The amount of adsorbed bovine serum albumin (BSA) onto the synthesized micrometer-sized Hap particles is strongly dependent upon their mean particle length (L p ), while that of lysozyme (LSZ) onto the Hap particles exhibited a minor dependence on the L p . This protein adsorption behavior observed in the present paper provided a definitive evidence that the C sites exposed on ac or bc crystal faces are the adsorption sites for BSA.