High tibial osteotomy is now an accepted procedure in the treatment of osteoarthritis of the knee. Since the effect of this procedure is to shift the line of weight bearing from one compartment of the other, the procedure is of value in knees with osteoarthritis only when there is predominant involvement of one compartment. The osteoarthritis of knee developed bilaterally in many case, so simultaneous bilateral high tibial osteotomy under one anesthetic was considered. Eight cases of osteoarthritis with genu varum deformity were treated by simultaneous bilateral high tibial osteotomy at the Department of Orthopaedic Surgery of NMC during the,period from January, 1984 to December, 1987. The results were as follows: l. All case were female, and the mean age was 56 years old. 2. Preoperative mean varus angle were 4° in right, 3.4° in left, and postoperative mean valgus angle were 8° in right, 6° in left at final follow-up. 3. The results after average 2.2 years of follow-up were as follows: good in 5 cases(63%), fair in 1 cases(12%), poor in 2 cases(25%) 4. The complications were one proximal tibial fracture, one displacement of distal fragment, and one transient peroneal nerve palsy. 5. Mean immobilization period was 7 wks and mean hospitalization period was 48 days. 6. More rigid internal fixation was recommended in simultaneous procedure to reduce the period of hospitalization and early ambulation.