Fatigue lifetimes tend to separate into two populations as the stress level is decreased. The short lifetime population, termed as the life-limiting distribution, is found to be largely controlled by the small + long crack growth lifetimes. The longer lifetime population, which tends to dominate the mean-lifetime, has an increasing contribution of the crack-initiation lifetime as the stress level is decreased. Fatigue lifetime distribution in Ti-6Al-2Sn-4Zr-2Mo was studied from the perspective of the life-limiting versus the mean behavior. The crack-initiation mechanisms in the life-limiting versus the mean-lifetime failures were characterized using quantitative tilt fractography and electron back-scattered diffraction analysis, and the results were compared to other titanium alloys. A modeling approach for predicting the probability of occurrence of life-limiting failures is discussed. The approach takes into account the hierarchy of randomly occurring microstructural combinations, which is suggested to produce a distribution in fatigue deformation levels leading to a probability of a critical level of deformation accumulation for crack initiation in a very few cycles. The approach is illustrated with the help of a single phase -titanium microstructure for which predictions of the probability of occurrence of the life-limiting failures were made with respect to the stress level and the specimen volume.