Acrylic bone cements are one of the most important biomaterials used in orthopaedic surgery and dental applications to fill the cavities or provide mechanical interlock between prosthesis and the bone. Their biocompatibility can be increased by addition of different materials into the formulation, such as hydroxyapatite. Besides all the advantages, bone cements have several drawbacks including tissue necrosis, chemical necrosis, shrinkage of the cement and aseptic loosening. Therefore painstaking research and study are carried out on development of new formulations to improve mechanical and thermal properties as well as biocompatibilities. In this study, bone cements with different compositions were prepared and new formulations were examined to improve mechanical properties and to reduce maximum curing temperature. It was observed that addition of hydroxyapatite, while keeping polymer-to-monomer ratio constant at 2.0, decreased curing temperature and increased compressive strength about 11% (Group-C) when hydroxyapatite addition was 12%. Further addition of hydroxyapatite destroyed homogeneity of the cement dough and made it difficult to handle. The composition which contains 8% hydroxyapatite was chosen as the optimum composition in respect of mechanical properties with 102.62&deg / C curing temperature. In order to decrease the curing temperature ammonium nitrate this gives endothermic reactions with water, was added into the formulations. Addition of 0.5 g NH4NO3 decreased curing temperature from 94&deg / C to 79.3&deg / C while compressive strength kept in acceptable range with 95.99 MPa. Experiments demonstrated that the proposed formulation is acceptable for workability, homogeneity, mechanical strength and thermal properties. Further studies especially on curing temperature and biocompatibility should be achieved.