The influence of alloying elements and the potential on the corrosion resistance of Pi and other Ti-based biomedical implant alloys under simulated physiological conditions is presented. Ti and its following alloys: Ti-10Mo, Ti-10Mo-10Al, Ti-7Al-4.5V and Ti-5Al-4.5V and Ti-5Al-2.5Fe were studied. Electrochemical impedance spectroscopy was used and the experimental results were compared with those obtained by potentiostatic and potentiodynamic techniques. All the measurements were made in Ringer's solution at pH 7.8 and at different potentials (E-corr, - 650, - 500, 0, + 200 and + 400 mV vs. SCE). Under these conditions, all the Ti-based alloys exhibited spontaneous passivity. It was evident that Mo, V and Fe improved passivity and limited the active corrosion of the beta-phase of Ti while Al enrichment of the alpha-phase was found to be detrimental to the passivity and corrosion resistance of Ti.