This prospective study was performed to evaluate the clinical and radiological results of radiocarpal joint arthrodesis in the treatment of unstable Simmen group III and Larsen grade II or III rheumatoid wrists. Radiolunate arthrodesis was performed in 16 wrists and radioscapholunate arthrodesis in 7 wrists in 20 patients. When they were evaluated at a mean of 5.8 (range 3.5-9.8) years later, flexion was 29 degrees and extension 34 degrees , representing 67% and 92% of the preoperative values, respectively. Patient satisfaction was excellent, or good, for 20 wrists and satisfactory for 1 wrist. In two patients with poor satisfaction, arthritis progressed to the midcarpal joint and necessitated total arthrodesis of the wrist. Radiolunate joint arthrodesis, with inclusion of the scaphoid in the fusion if necessary, is a useful operation in the treatment of this degree of wrist disease as it produces a functional and pain-free wrist at the same time as preserving much of the mobility and bone stock.