This book deals with a biomaterial, hydroxyapatite (HAP), its physical and chemical properties and technological applications as implant coating, antimicrobial agent, catalysis, chromatographic separation of proteins and DNA, drug delivery carrier and non-viral vector as gene therapy. It also covers different aspects of HAP study like bio-mimetic study, hemolysis study. It also covers the synthesis and characterization of pure HAP nano - particles and silver-doped nano HAP. The nano-particles of HAP are synthesized using surfactant mediated approach and characterized by powder XRD, TEM, FTIR, TGA, and dielectric study.