The effects of calcium fluoride (CaF2) additions on the densification and mechanical properties of hydroxyapatite-zirconia composites (HA-ZrO2) were investigated. When small amount of CaF2 was added, the density of the composites was markedly enhanced. The reactions of HA with CaF2, which led to the formation of fluorapatite (FA), were attributed to the observed improvements in densification. When HA-20-vol%-ZrO. composites were sintered, with the addition of 5 vol% of CaF2. in air at 1300degreesC, the density of the specimen approached 98% of the theoretical value. The flexural strength and fracture toughness of the composites were also improved, as a result of the enhanced densification.