We wish to gain a deeper understanding of where dopant cations and anions reside in hydroxyapatite (HA). We will substitute Sr, Si, 11B and S into the HA structure and determine which sites in the unit cell each dopant preferentially occupies. Data such as shifts in interatomic distances or distortions to PO43- tetrahedral would also be useful. Such information cannot be obtained by simple XRD analysis (figure 1). However, by understanding how the charge and ionic radius of dopants ions dictates where they reside in mono-substituted HAs, we believe we can more quickly tailor novel substituted HAs to deliver a specific type of bioactivity behaviour. This increased understanding allows for improved experimental design and research efficiency when developing next generation bioceramics for applications in orthopaedic fields.