Dual angles has been applied to study the kinematics of mechanical systems. In this paper a modification of the Euler angle formulation, which uses dual angles, is applied to the study of the general three-dimensional kinematics of human joints. The method estimating dual Euler angles from spatial coordinates of markers using least-squares algorithm is also given. In analogy with Euler angles, dual Euler angles follow anatomical movement patterns. Moreover, this method can describe general spatial joint movement.