The authors investigate how the density and mechanical properties of green and sintered hydroxylapatite specimens depend on the pressure of cold isostatic pressing (CIP). It is shown that as the CIP pressure grows, the density, the ultimate bending strength, and the fracture toughness in green specimens increase to reach 2.70 g/cm3, 50 MPa, and 0.8 MPa·m1/2, respectively, at 2.0 GPa. The maximum value of the ultimate bending strength of the sintered material is 120 MPa at a density of 3.02 g/cm3. A qualitative explanation of the observed phenomena is suggested.