Ca0-MgO-P2O5-SiO2-F- glass-ceramic which contains apatite and mica crystalline phases can be used to repair and reconstruct diseased or damaged bones and teeth because of their biocompatibility and bioactivity. Like other glass-ceramics, the mechanical properties of material depend on their microstructure. In this paper, the relationship between the microstructure and the mechanical properties of CaO-MgO-P2O5-SiO2 glass-ceramics containing fluorophlogopite and fluorapatite was analyzed with DTA, SEM, XRD techniques and some mechanical testing methods. The results showed that the sample heated at 810 degreesC for 4 h had smaller crystalline size and less volume fraction of fluorophlogopite, so it had higher bending strength (190 MPa) and higher crack toughness (2.63 MPa.m(1/2)). (C) 2003 Elsevier Ltd and Techna S.r.l. All rights reserved.