Proponents of tourniquets postulate that they optimise intra-operative visibility and reduce blood loss. This study compared the outcomes of tourniquet assisted to non-tourniquet assisted total knee replacement (TKR). A systematic review was undertaken of the electronic databases Medline, CINAHL, AMED and EMBASE, in addition to a review of unpublished material and a hand search of pertinent orthopaedic journals. The evidence-base was critically appraised using a tool from the Cochrane Bone, Joint and Muscle Trauma Group. Fifteen studies were identified evaluating 16 outcome measures and parameters of 1040 TKRs in 991 patients. There was a significantly greater intra-operative blood loss in non-tourniquet compared to tourniquet assisted surgery (p=0.004). There was no significant difference between the groups for total blood loss or transfusion rate (p=0.22; p=0.48). There was a trend for greater complications in tourniquet compared to non-tourniquet patients. There was no difference between the groups for any other outcome measure assessed. In conclusion, this systematic review has found that there is no advantage to using a tourniquet in knee replacement surgery for reduction of transfusion requirements.