The high cycle fatigue (HCF) behavior of Ti–6Al–4V is investigated for cylindrical specimens having three sizes of geometrically similar circumferential V-notches, each with an elastic stress concentration factor, Kt, of approximately 2.78. A step loading technique for obtaining a point on a constant life (106 cycles) Haigh diagram from a single test specimen was implemented. Tests were performed at stress ratios of R=0.1, 0.5, and 0.8 for specimens machined from two different product forms of Ti–6Al–4V, bar and plate forgings. Results indicate that while there is a definite notch size effect in the Ti–6Al–4V bar within the range of notch sizes tested, little or no such effect exists in the plate.