Fatigue performance is the limiting factor in many applications of advanced alloys. However, fatigue testing is costly and time-consuming and provides almost no information on what in the material is controlling fatigue life, and therefore testing is only of limited value when it comes to improving the fatigue performance of the material. It is now widely accepted that, after yield strength, fatigue life is mainly dictated by the microstructure. Over the past decade, crystal plasticity modelling has been extensively used to model the crack initiation in alloy microstructures [1], in an effort to enhance our understanding and enable improvements in fatigue performance through microstructural control. In this approach, values of local stress and strain are used to predict the location of crack initiation using the concept of fatigue indicator parameters. Although this approach relies on the accurate, or at least representative, calculation of local stresses and strains at the microstructural scale, the models used are invariably only calibrated, and validated, at the macroscopic scale only. There are only a few attempts at trying to validate these predictions at the microstructural scale. Here we present the results of a number of recant attempts to validate model predictions at the microstructural scale. High resolution digital image correlation was used to measure the strain distribution with sub-micro resolution during the onset of yield and beyond. Measurements were done during monotonic and cyclic loading, in titanium and nickel based aerospace alloys. The results were compared with crystal plasticity models, both using image based models and statistically representative models. This work showed that the crystal plasticity predictions of slip activity and strain localization are very different from those measured experimentally. The implications of these results to the applicability of crystal plasticity modelling to the prediction of the effect of microstructure on fatigue life are discussed. [1] D.L. McDowell, F.P.E. Dunne, Microstructure-sensitive computational modeling of fatigue crack formation, International Journal of Fatigue. 32 (2010) 1521–1542.