Dislocation of the total artificial hip is the second most common cause of failure of this otherwise very successful surgery. Dislocation is caused by an impingement and lever-out mechanism, where the impingement point constitutes a fulcrum around which the femoral component is levered out of articulation with the acetabular component. It is a painful and costly complication, effecting from 2-11% of primary surgery patients and from 4-25% or more of patients who undergo revision surgery. Systematic study of implant design changes has not been performed to any great extent. A computational model has been developed using the finite element method, to simulate the phenomena of impingement and dislocation. This model is a fully non-linear, three-dimensional, sliding contact model with non-linear material characteristics for the polyethylene bearing insert of the total hip construct. The model simulates the impingement of the femoral neck on the lip of the acetabular component. Experimental validation showed that the model gives very accurate predictions of range of motion to impingement and dislocation, as well as of the moment developed to resist dislocation. An extensive array of parametric series has been run investigating the effects of various design changes on the stability of the total hip construct. By and large, these tests were run under physiologic loading conditions of a 942 N hip contact force and a simulated erectly seated leg cross maneuver, involving a combination fo flexion and adduction. The data showed that, in many cases, there is a trade off of stability versus range of motion for many design parameters. Design changes which increase stability, i.e., maximum resisting moment developed, have the effect of lessening the allowable range of motion prior to impingement and dislocation. This also works in reverse, where changes which allow more range of motion generally lead to less stability, or to a lower resisting moment being needed to dislocate. A new total hip design has also been investigated. This new system was shown to improve the resistance to posterior dislocation from an erectly seated leg cross, and to lessen contact stresses during impingement.