The importance of determining and understanding the very high cycle fatigue behaviors of materials has gained strength in recent years. Ti-alloys, in view of their high strength-to-weight ratio, have a range of structural applications. Of these, Ti-6Al-4V, belonging to the alpha-beta type is the most widely used. The present paper deals with investigations on the fatigue behavior of TC4, the Chinese equivalent to Ti-6Al-4V, up to very high cycles. Fatigue testing was carried out on a piezoelectric ultrasonic fatigue machine operating at 20 kHz frequency. Hourglass shaped resonant specimens were tested in ambient air at room temperature under completely reversed loading conditions (R = -1). Failure in the alloy was seen to occur right up to the gigacycle regime, with the fractures being found to initiate from the surface unlike in steels. The fracture surfaces exhibit brittle characteristics containing river patterns and cleavage facets, as well as striations.