Introduction : Radius shortening is well accepted useful treatment for the Kineböck's disease with ulna minus variance. However, ulnar abutment syndrome may be induced if this procedure is indicated to the Kienböck's disease with ulnar zero or plus variance. Radius wedge osteotomy does not require to change ulnar variance, however the opposite procedures of opening and closing osteotmy have been recommended. Based on our cadaveric experiment, we have applied 8°opening wedge osteotomy for the Kieneböck's cases with ulnar zero or plus variance since October 1986. Methods : Radial open angle of 8 degrees was aimed at operation in all patient. In the early cases, K-wire fixation was used and AO T-plate in the recent cases with iliac bone grafting. Patients : We have applied opening wedge osteotomy for 20 patients (10 males and 10 females). Follow-up time of 18 patients ranged from 3 to 14 years with an average of 9 years and 6 months. Age at operation ranged from 30 to 72 with an average of 50. Preoperative ulnar variance was plus with an average +1.2mm in 14 cases and there were 4 cases with ulnar zero-variance. Results : Radial open angle was obtained postoperatively in 10 patients and the angle ranged 3 to 10°with an average of 7°. In the other 8 cases, radial closing of 0 to 10°was resulted with an average of 5° closing. Postoperative ulna variance did not change in 11 cases and increase in ulnar variance (1mm in average) in the other 7 cases at the time of the latest follow-up. These patients were assessed using Nakamura's evaluation method. In the open angle groups, 9 cases were rated as excellent and 1 as good (average score 26.4). In the radial closing or unchanged angle group, 2 cases were evaluated as good and 7 cases as fair (average score 17). There was a statistically significant difference between these two groups. Discussion : Nakamura et al reported the results of radial closing wedge osteotomy for the 21 Kineböck's cases with ulnar zero or plus variance. The average score of these cases rated 18.6 which was similar to that of radial closing or unchanged group in our series. The radial opening wedge osteotomy requires relatively stable fixation, however if the aimed 8°open angle is attained, excellent results can be expected.