The purpose is to demonstrate that Bi-Unicom- partmental knee arthroplasty (Bi-Uni) can produce equivalent long-term outcomes to total knee arthroplasty (TKA) in patients with bicompartmental knee osteoarthritis involving both the medial and lateral tibio-femoral compartments. A total of 37 patients with bicompartmental tibio- femoral osteoarthritis of the knee treated between January 1999 and March 2005 underwent either Bi-Uni or TKA. Nineteen patients who underwent simultaneous implantation of 2 unicompartmental knee arthroplasties (UKA) were matched and compared with 18 patients who had undergone a computer assisted TKA. At latest follow-up no statistically significant differences were seen between the 2 patient groups for KSS, Function scores and WOMAC Arthritis Index (pain score). The patients undergoing Bi-Uni did showed a statistically significant superior outcome for function (P < 0.05) and stiffness (P < 0.01) WOMAC indexes compared with the TKA group. The results of this study suggest that Bi-Uni is a valid alternative to address medial and lateral tibio- femoral osteoarthritis of the knee in selected cases. Bi-Uni replacement produces results equivalent TKA in patients with bicompartmental knee osteoarthritis involving both the medial and lateral tibio-femoral compartments and could represent a new frontier in modern knee reconstructive surgery. Level of Evidence: Level IV, retrospective comparative study.