Although high tibial osteotomy for osteoarthrosis of the knee joint is well recognized, its place in the management of rheumatoid arthritis of the knee is much less well established. Thirty-six rheumatoid knees were reviewed 1 to 6 years following tibial osteotomy. The results were 42 per cent good, 19 per cent satisfactory and 39 per cent poor. No patient remained free of pain for more than 3 years, and recurrence of pain was not always associated with recurrence of deformity. Varus knees did considerably better than valgus knees despite some technical errors. Maintenance of a normal femoro-tibial angle range of 164 degrees to 177 degrees at follow-up was important but not as vital as in osteoarthrosis of the knee. The beneficial effect of tibial osteotomy in rheumatoid arthritis of the knee seldom lasted more than 3 years after which time an increasing number of bad results were seen. It was concluded that high tibial osteotomy was a satisfactory procedure for rheumatoid arthritis of the knee but its efficacy was not comparable to that seen in osteoarthrosis nor was its effect long-lasting.