Hydroxyapatite (HAP), described by the formula Ca10(PO4)6(OH)2, is one of the inorganic components of the hard tissues of living bodies such as bones and teeth. HAP is a calcium phosphate-based bio-ceramic, which has been used for several years in medicine and dentistry because of its excellent biocompatibility with human tissues. The success of its application in these fields depends upon factors such as the composition, crystallinity, size and morphology of HAP particles. This paper describes the work performed regarding the synthesis of this compound by a wet method comprising the direct precipitation of orthophosphoric acid solution to a calcium hydroxide solution, the process being described by the following reaction: 10 Ca(OH)2 + 6 H3(PO4) <=> Ca10(PO4)6(OH)2 + 18 H2O. Synthesis was performed in a laboratory reactor, 700mL in capacity, which was instrumented and controlled using a computer interface, so that the influence on process variables, such as reaction temperature, pH, medium inertization by N2, velocity of stirring and the flow rate input of H3(PO4), could be assessed. The influence of these parameters was, therefore, evaluated in terms of the required composition and morphology of HAP formed particles. The particles were analysed by FTIR, XRD, SEM and EPMA for the determination of the Ca/P ratio. From the obtained results, it can be concluded that HAP particles, having suitable properties for use in medicine, could effectively be prepared by this technique, provided that a good control of the involved process variables is maintained.