Abstract: A two-degree-of-freedom spherical shoulder joint for a robot. The joint consists of a spherical ball member with gear teeth formed in its outer surface and three drive gears that mate with the gear teeth in the outer surface of the spherical member. The joint can rotate about any axis of rotation which lies within a plane defined by the contact points between the drive gears and the spherical member. By controlling the three drive gears to rotate by the proper amounts, the joint can be rotated about the desired axis of rotation. The inverse kinematics for controlling the joint are described.