The effects of an addition of monoclinic ZrO 2 into the Ti/2B system were studied in order to control the exothermic reaction. Thermal histories of the phase formation in both Ti/2B and Ti/2B/20 vol.% ZrO 2 system were investigated by High Temperature X-ray Diffraction (HTXRD) accompanied with differential thermal analysis (DTA) under a flowing argon atmosphere. The results indicated that ZrB 2 formation was initiated at about 900 o C prior to TiB 2 formation in the ZrO 2 added compositions. A two-step borothermic reduction of ZrO 2 is believed to yield liquid boron oxide as an intermediate phase. Actual combustion synthesis experiments were carried out for the same compositions under a vacuum atmosphere. Ti/2B samples ignited easily and the reaction front propagated quickly while the ZrO 2 added samples were hard to ignite and the propagation was slow. Controlled reactions were achieved due to the formation of glassy B 2 O 3 during the borothermic reduction of ZrO 2 . SEM microstructures showed that B 2 O 3 flowed into the pores thus dissipating the heat away. X-Ray diffraction patterns taken at room temperature after the ignition, showed TiB 2 as the major phase for the Ti/2B composition and ZrB 2 and TiB 2 as the major phases for the ZrO 2 added compositions.