Forty-eight revision total knee arthroplasties (TKAs) for failed unicompartmental total knee prostheses were evaluated at 5.4 +/- 2.5 years after revision. The most frequent mode of failure of the original arthroplasty was loosening. All revisions used a condylar-type prosthesis. Fifty percent of the knees had bone defects that were filled with cement. Good or excellent results were achieved in 81% of the knees. One knee had a complete radiolucent line adjacent to the tibia at last evaluation. The surgical complication rate was 13%. Predictable salvage of the failed unicompartmental TKA can be achieved by revision arthroplasty.