Posterior-stabilized and posterior cruciate retaining total knee arthroplasty prostheses have had high success rates, but it is unclear whether one design has superior outcomes. The purpose of the present study was to directly compare the outcomes of these two designs. Forty-five patients who received a posterior-stabilized prosthesis were compared to 46 consecutive patients who received a cruciate-retaining implant. At a mean follow-up time of 60 months (range, 49 to 69 months), the mean Knee Society knee scores improved from 42 points (range, 20 to 73 points) to 93 points (range, 39 to 100 points) for the cruciate-retaining group and from 38 points (range, 20 to 70 points) to 94 points (range, 60 to 100 points) for the posterior-stabilized group. The mean Knee Society functional scores improved from 36 points (range, 10 to 60 points) to 71 points (range, 15 to 100 points) for the cruciate-retaining group and from 32 points (range, 10 to 70 points) to 73 points (range, 32 to 100 points) for the posterior-stabilized group. The ranges of motion were 125 degrees (range, 100 to 140 degrees ) and 118 degrees (range, 87 to 135 degrees ) in the cruciate-retaining and posterior-stabilized groups, respectively, at final follow-up. Radiographic analysis revealed no radiolucencies that were progressive or were greater than 1 millimeter in length. There were no re-operations in either group. This study did not conclusively demonstrate the superiority of one knee design over the other, suggesting that the choice of implant should be based on surgeon preference and existing pathology of the posterior cruciate ligament.