Wrong alignment of hip and knee prosthesis is a known risk factor for early loosening and revision. Meta-analyses have shown that, by use of computer navigation, outliers can be reduced significantly. Our analysis of 200 implanted knee prostheses (100 navigated procedures, 100 conventional procedures) and 60 implanted hip resurfacings (30 navigated procedures, 30 conventional procedures) yielded the same result: In total knee arthroplasty and hip resurfacing, the numbers of outliers were significantly reduced by use of computer navigation. Furthermore, in total knee arthroplasty a significantly reduced blood loss and need for blood transfusions were noted if computer navigation was used. Long term studies are required to verify if computer navigation may be an economically cost-saving procedure. So far, in our clinic every navigated operation produced extra costs of 442 Euros. In our current healthcare system no reimbursement for these additional charges exist.