Alumina (α-Al₂O₃) is a ceramic oxide material that has been used as a biomedical implant material since the early 1970s in both high-density, high-purity polycrystalline and single crystal forms. The composition and microstructure of alumina are strongly dependent on the manufacturing processes used to make components and can profoundly influence the performance of the material in service. The purification and refinement of alumina powder and conventional ceramic fabrication routes used to manufacture alumina components are examined. The role of chemical composition and microstructure on the strength, fracture behavior, fatigue, and wear behavior of high-density, high-purity polycrystalline alumina are examined with specific reference to the use of this material in load-bearing tribological applications in biomedical engineering. Regulatory requirements governing the use of alumina as an implant material, in particular the need for the ceramic to be fully dense and to have small grain size in order for it to be used reliably in total hip prostheses, are explained by consideration of the underlying materials science as well as the clinical demands in service. The biocompatibility of alumina, the use of osseous tissue ingrowth to stabilize prostheses in the skeletal system, and the application of polycrystalline alumina and sapphire in dental applications are also examined.