1. A technique of arthrodesis of the trapezio-metacarpal joint of the thumb is described. Primary fusion was achieved in thirty-six of thirty-nine cases.

2. Compensatory movement at the adjacent joints permits a good range of thumb movement.

3. Trapezio-metacarpal arthrodesis is the operation of choice for patients under fifty with isolated osteoarthritis of this joint. It is also useful for stabilising the thumb in patients with paralysis of the thumb when adequate muscles for transfer are not available.