Ceramics used for medical purposes are known as bioceramics, such as hydroxyaptite (HA), which is one of the most well studied bioceramics because of its similar composition to human bone and also good biocompatibility, is bioactive and has excellent osteoconductivity. In addition many properties of HA can be improved by the addition of specific elements into its structure.The research in this thesis investigates the substitution of some selected elements into the structure of HA and subsequent characterisation in terms of physical, mechanical and biological responses. Si/S-HA and Sr/B/S-HA was obtained from Lucideon and Ho/HA was synthesised in house.Initially a cell response to a variety of element oxides was performed to identify elements to avoid or potentially use for substitution. Dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho) and praseodymium (Pr) at 100 ppm showed better results for alkaline phosphatase activity than 25 ppm in culture medium.2.5 and 5 mol.% of Ho was substituted into HA structure using a wet chemical method of synthesis. The samples were sintered at 1200°C for 10 hours. There was high crystallinity when 2.5 mol.% of Ho was added into the HA structure. Substitution of Ho in HA structure had the effect of shortening in a axis and elongation in c axis along with the higher concentration of Ho ion.2 mol.% of Si and S was also substituted into HA structure, where both elements Si and S replace PO4 site in HA structure. Si substituted in SiO4 form and S substituted in SO4 form for PO4 as confirmed by FT-IR results. Osteoblast-like cells cultured on Si/S-HA showed an increase in alkaline phosphatase, collagen type I and ostecalcin on samples sintered at high temperature.Sr/B/S-HA was also made where 2 mol.% of each element was substituted into the HA structure. The best condition of sintering temperature for Sr/B/S-HA was 1100°C for 10 hrs due to the resulting small grain size, improved cell adhesion and more collagen and osteocalcin production.These results suggest that the substitution of elements into the HA structure can provide novel bioceramics for control of physical mechanical and cell responses properties.