Molybdenum silicides were obtained by the self-propagating synthesis (SHS) method. Diamond composites containing 30 mass% of MoSi2 or Mo5Si3 bonding phase had been prepared using HT-HP Bridgman type apparatus. Sintering of the diamond composites were carried out at 2073 +/- 50 K and 8 +/- 0.2 GPa. The interactions in diamond-silicide composites were studied by means of X-ray diffractometry and transmission electron microscopy (TEM). Results of both mechanical properties and thermal resistance measurements are reported. Hardness HV1 for the composite with the predominantly MoSi2 bonding phase was found to be around 42 GPa. After heat treatment in 1200 degrees C for 30 min. in vacuum HV1 decreases to 29 GPa. In the second composite containing the Mo5Si3 bonding phase the HV1 of 28.0 GPa after thermal exposure changes to 21.0 GPa.