X-ray microbeams have been used to perform nondestructive measurements of the local orientations and microstructure in single-crystal and grain-boundary regions in a columnar Al (0.2 wt.% Mg) tri-crystal deformed 20% in plane-strain. The measurements were made using a recently developed differential-aperture X-ray microscopy (DAXM) technique providing high angular resolution determinations of local orientations with micron 3-D spatial resolution using focused microbeams. The X-ray microbeam technique is described, three-dimensional spatially resolved pole-figures and lattice rotation distributions in single-crystal and grain-boundary regions are presented, and the potential of micron resolution 3-D X-ray structural microscopy for plastic deformation investigations is discussed.