Three-dimensional deformation is necessarily associated with oblique plate convergence and commonly results in partitioning of deformation between contractional and transcurrent components along plate margins. Kinematic models of strike-slip partitioning for transpression and transtension allow the exact relation among three critical parameters---plate motion, instantaneous strain axes, and degree of strike-slip partitioning---to be calculated. Application to two end-member tectonic environments characterized by a low (South Island, New Zealand) and high (central California) degree of strike-slip partitioning demonstrates a remarkable consistency among the three parameters, suggesting that strike-slip partitioned transpression is a valid model for deformation in these regions. The extreme degree of strike-slip partitioning in wrench-dominated systems, such as central California, is tentatively associated with a fundamental misorientation of finite and instantaneous strain axes.