The deformation characteristics of a beta-type Ti-29%Nb-13%Ta-5%Zr alloy, developed for biomedical application, and their relation with the microstructure are investigated. The cold-rolled specimen is subjected to a tensile test at high temperatures ranging from 700 to 800 degrees C under a constant cross-head speed ranging from 1x10(-4) to 1x10(-2) s(-1). The elongations tested at different temperatures are compared with that of Ti-15%V-3%Cr-3%Sn-3%Al, a typical beta titanium alloy. The deformation mechanism is characterized from the parameter of the strain rate sensitivity. The microstructures before and after the tensile test are observed with optical microscope and the correspondent grain sizes are measured. The grain growth during the deformation is also described.