The ability to quantitatively measure crystallographic slip processes in-situ as a crystal plastically deforms is critical for the advancement of micromechanical models. In this work, new experimental X-ray diffraction techniques and analysis methods are implemented to study heterogeneous slip in deforming single crystals. An analysis method combining experimental data with simulations is first used to identify the active slip system in a deforming crystal, as well as information about the spatial gradients of slip present. A new method for quantifying the amounts of heterogeneous slip on multiple slip systems using single crystal pole figures is also developed. The method is applied to the study of single crystal pole figures measured in-situ from a plastically deforming silicon single crystal. Lastly, the results from a new high resolution diffraction technique are reported. In the experiment, three dimensional distributions of diffracted intensity are measured from a copper single crystal as it plastically deforms. A novel finite element based processing method is developed to extract quantitative information about the response of the lattice from the diffraction data. A combination of experimental and simulation results provide insight into how sharp gradients of slip influence the development of misorientation in a deforming crystal.