There are two classifications of femoral implants ñ cemented and cementless. The object of this study was to assess the effect of bone viscoelasticity on cemented and cementless implant stability. A cemented implant design was evaluated via a 3-D FE model. The results showed a small 1.41% increase in stem subsidence with inclusion of bone viscoelasticity. This is explained by the low stresses at the cement-bone interface. A 2-D FE model was utilized to evaluate the effects of coefficient of friction, press-fit and bone viscoelasticity on stem fixation. The push-out load increased with µ for each value of δ, but minimal increases in the push-out load (2.9% to 4.9%) were observed for δ > 0.10mm. Bone viscoelasticity reduced the push-out load (2.6% to 82.6%) in all cases. It is concluded that there is a ìthresholdî with respect to the degree of press-fit beyond which no additional gains in fixation are achieved.