We study the influence of solid-solution hardening (by the method of thermal-diffusion saturation from a rarefied oxygen-containing atmosphere) of the surface layers of VT1-0 titanium alloy on its fatigue resistance in bending with rotation. It is shown that the dependence of fatigue limit on the degree of surface hardening has a maximum whose value depends on the depth of the hardened zone. We managed to increase the original fatigue limit of the alloy by 38% for a relative increment of the surface hardness K of 70% and a depth of the hardened zone l of 30 µm.