The aim of the present paper is to investigate the combined effect of mold material and binder for investment casting of titanium and titanium alloys. A plasma arc melting furnace was used for melting titanium alloy, and the interfacial reaction of titanium castings was determined by optical microscope, SEM, EDS analysis and hardness profile. The mold materials examined were ZrO₂, Al₂O₃, CaZrO₃ and CaO. Machined graphite mold was examined for comparison. The result shows that the titanium castings produced using ZrO₂ and Al₂O₃ mold had a clear reaction whereas a negligible reaction occurred in the castings in CaO, CaZrO₃ and graphite molds. CaZrO₃ is regarded as a promising mold material for titanium castings from the viewpoints of thermal stability against molten titanium alloy, sufficient mold handling strength and slurry viscosity control.