The　variations　of　microhardness　and　microstructures　for　the　biomedical　Ti-35Nb-5Ta-7Zr　and　Ti-35Nb-7Zr　alloys　subjected　to　different　heat　treatments　were　studied　by　microhardness　test,　X-ray　diffractometry　and　transmission　electron　microscopy.　The　effects　of　alloying　element　Ta　on　these　variations　and　aging　precipitation　sequences　were　revealed.　The　results　show　that　the　aging　strengthening　effect　in　the　Ti-35Nb-5Ta-7Zr　alloy　is　more　prominent　than　that　in　the　Ti-35Nb-7Zr　alloy.　For　the　solution-treated　Ti-35Nb-5Ta-7Zr　and　Ti-35Nb-7Zr　alloys　(in　ST　state),　the　precipitation　sequences　during　subsequent　aging　treatments　at　300　and　600°C　can　be　described　as　β+α″(ST)　(300°C)→β+α(600°C)→　β+α+isothermal　ω　for　the　former,　and　β+α″+quenched　ω(ST)(300°)→β+α+isothermal　ω(600°)→β+α　for　the　latter.　The　addition　of　Ta　to　the　Ti-Nb-Zr　alloy　system　can　suppress　the　formation　of　quenched　ω　phase　during　the　solution　treatment　and　increase　the　precipitation　temperature　of　the　isothermal　ω　phase　during　subsequent　aging　treatments.