Self-setting calcium phosphate cements (CPC) consisting of hydroxyapatite (HA) and tetracalcium phosphate were reinforced with various amounts of hydrothermally synthesized HA whiskers with an aspect ratio of 10. Flexural strength (sigma(b)) and work of fracture (gamma(wof)) were calculated by four-point bending tests, and fracture surfaces were analyzed by scanning electron microscopy (SEM). sigma(b) and gamma(wof) of the CPCs that were reinforced with 30 vol% HA whiskers increased by 60% to 7.4 MPa and by 122% to 102 J/m(2), respectively. SEM analyses reveal that this increase could be correlated to energy-dissipating processes (e.g., whisker pull-out) at the crack tip.