While dislocation is a leading cause of total hip replacement failure, empirical observations far outnumber systematic laboratory examinations of this phenomenon. A previously validated three-dimensional, non-linear, contact finite element model was used to study how surgical placement affects dislocation propensity. The computational model employed a widely used 22mm modular system, and examined range of motion prior to impingement as well as peak moment developed to resist dislocation under a typical leg-crossing maneuver. Results were compared to a previous study of an otherwise similar 26mm modular head system, using the same formulation. Similar trends occurred. Increasing tilt and/or anteversion increased both the range of motion and the peak resisting moment, while apparent stiffness seemed to be unaffected. Further, impingement range of motion was independent of head size, but peak resisting moment was nearly 25% less for the 22mm head sizes.