High-purity tantalum single crystal cylinders oriented with  parallel to the cylinder axis were deformed 10, 20, and 30 percent in compression. The engineering stress-strain curve exhibited an up-turn at strains greater than ∼20% while the samples took on an ellipsoidal shape during testing, elongated along the  direction with almost no dimensional change along . Two orthogonal planes were selected for characterization using Orientation Imaging Microscopy (OIM): one plane containing  and  (longitudinal) and the other in the plane containing  and  (transverse). OIM revealed patterns of alternating crystal rotations that develop as a function of strain and exhibit evolving length scales. The spacing and magnitude of these alternating misorientations increases in number density and decreases in spacing with increasing strain. Classical crystal plasticity calculations were performed to simulate the effects of compression deformation with and without the presence of friction. The calculated stressstrain response, local lattice reorientations, and specimen shape are compared with experiment.